Tool Guides & How-Tos
Step-by-step guides for our free generators, calculators, and checkers. Learn the concepts, then open the tool — no signup required.
All guides
How Absolute Value Works (And How to Calculate It)
Learn absolute value |x| as distance from zero, number-line views, equation solving, and properties — with clear examples and a free calculator.
Read guideHow Annuity Payments and Present Value Work
Learn ordinary vs annuity due, present and future value formulas, payment streams, and retirement context so you can read annuity math with clear numbers.
Read guideHow APY Works and How to Compare Savings Rates
Learn APY vs APR, how compounding frequency changes yield, effective annual return on savings and CDs, and how to compare bank offers with a free APY calculator.
Read guideHow Base64 Encoding Works (And When to Use It)
Learn what Base64 is, why it adds ~33% size overhead, how encode and decode work, URL-safe variants, data URIs, and why Base64 is not encryption.
Read guideHow Binary Arithmetic Works (Add, Subtract, Multiply)
Learn binary addition, subtraction, multiplication, multi-base results, bits and overflow, and CS basics with a free binary calculator.
Read guideHow Coin Flips Work for Random Decisions
Learn 50/50 probability, multi-coin statistics, fairness, and when a digital coin flip helps you choose without bias online.
Read guideHow Color Blindness Screening Tests Work
Learn how Ishihara-style plates screen for protan, deutan, and tritan color vision differences — and why online tests are not a medical diagnosis.
Read guideHow Credit Card Number Validation Works (Luhn)
Learn the Luhn checksum, IIN/BIN network prefixes, client-side card checks, and why validation is not payment processing or proof a card is real.
Read guideHow Cron Expressions Work (And How to Build Them)
Learn the five cron fields (minute, hour, day, month, day-of-week), common schedules, and how to translate expressions into plain English.
Read guideHow Factorials Work (And How to Calculate n!)
Learn what n! means, why 0! = 1, how factorials drive permutations, how fast they grow, and how to calculate them with clear steps.
Read guideHow GUIDs and UUID v4 Identifiers Work
Learn GUID and UUID v4 structure, braces and case options, bulk generation, and when random IDs beat sequential counters in apps and databases.
Read guideHow Hash Functions Work (MD5, SHA-256, and More)
Learn one-way hashing, MD5 vs SHA-256, integrity checks, why hashes are not encryption, and how to generate digests safely in the browser.
Read guideHow IMEI Numbers Work and How Test IMEIs Are Built
Learn the 15-digit IMEI format, TAC structure, and Luhn checksum used for test data — for development only, never for fraud or device spoofing.
Read guideHow Life Expectancy Estimates Are Calculated
Learn actuarial tables, lifestyle risk adjustments, and why life expectancy is a population estimate — not a personal prophecy. Free tool.
Read guideHow Linear Regression Finds a Best-Fit Line
Learn least-squares linear regression: slope, intercept, R², correlation, residuals, and predictions — free regression calculator guide.
Read guideHow Long Division Works (Step by Step)
Learn the long division algorithm with clear steps for quotient, remainder, decimals, and mixed numbers — plus how to check work and teach the method.
Read guideHow Much House Can You Afford?
Learn DTI limits, income and debt inputs, down payment impact, max home price math, and how taxes and insurance change what you can safely buy.
Read guideHow One-Sample T-Tests Work in Hypothesis Testing
Learn one-sample t-tests: null hypotheses, t-statistics, p-values, and one- vs two-tailed tests — with clear steps and a free calculator.
Read guideHow Ovulation Calculators Estimate Fertile Days
Learn how LMP, cycle length, and the luteal phase model estimate ovulation and the fertile window — educational only, not medical advice.
Read guideHow Roth IRA Growth Works Over Time
Learn tax-free Roth IRA growth, contribution limits, Roth vs traditional basics, and long-horizon projections with compound returns — free online.
Read guideHow Scientific Notation Works
Learn a×10^n scientific notation, engineering form, E-notation, and how to handle huge or tiny numbers — with examples and a free converter.
Read guideHow Simple and Compound Interest Work
Learn simple vs compound interest, the P(1+r/n)^(nt) formula, compounding frequencies, growth charts, and when to use each — free online.
Read guideHow to Add, Subtract, and Calculate Work Hours
Learn time arithmetic for hours and minutes, timecard totals, overnight shifts, overtime, and 12h vs 24h formats — free online.
Read guideHow to Build a Balanced D&D 5e Encounter
Build XP-balanced D&D 5e combat encounters: party level thresholds, CR budgets, monster multipliers, difficulty tiers, and free generator steps.
Read guideHow to Build a Dome in Minecraft
Build Minecraft domes layer by layer: radius, hollow vs solid, dome with floor, block counts, blueprints, and WorldEdit shortcuts — free generator.
Read guideHow to Build a Sphere in Minecraft Layer by Layer
Learn voxel sphere radius, hollow vs solid builds, hemispheres and domes, block counts, and WorldEdit shortcuts — with free layer-by-layer blueprints.
Read guideHow to Build Minecraft Commands Without Syntax Errors
Learn give, summon, effect, and more with target selectors and Java vs Bedrock differences so you can paste working Minecraft commands without chat errors.
Read guideHow to Calculate & Interpret Your BMI
Learn the BMI formula, metric and imperial steps, adult category ranges, healthy weight estimates, and real limits of BMI — then calculate yours free online.
Read guideHow to Calculate a Weighted Grade
Learn category weights, percentage vs points modes, final score formulas, and letter-grade conversion so your syllabus average matches what you expect.
Read guideHow to Calculate a Z-Score
Learn the z-score formula z = (x − μ) / σ, percentiles on the normal curve, reverse lookup, and when standardized scores help — free tool.
Read guideHow to Calculate Aspect Ratios for Images and Video
Learn 16:9, 4:3, and 1:1 ratios, proportional scaling, and GCD-reduced forms so you can size images and video without distortion.
Read guideHow to Calculate CD Interest and Build a CD Ladder
Learn CD compound interest, APY vs APR, term tradeoffs, early withdrawal penalties, and how to build a CD ladder — then run the numbers free online.
Read guideHow to Calculate Days Between Two Dates
Learn how to find days between two dates, add or subtract days, count business days, and use age mode — free online guide.
Read guideHow to Calculate Discounts and Sale Prices
Learn percent-off math, sale price from original, reverse original from sale, stacked coupons, and tax after discount — with clear examples and a free tool.
Read guideHow to Calculate Electricity Cost for Appliances
Learn watts, kWh, utility rates, and daily/monthly/yearly cost formulas so you can estimate any appliance’s share of your electric bill.
Read guideHow to Calculate Exact Age From a Date of Birth
Learn to calculate exact age in years, months, and days, measure time between dates, and track birthday countdowns with precision — free online.
Read guideHow to Calculate Fuel Cost for a Trip
Learn trip fuel math: distance, MPG vs L/100km, fuel price, round-trip totals, and cost per mile so you can budget any drive before you leave.
Read guideHow to Calculate GCD and LCM
Learn GCD and LCM with the Euclidean algorithm, prime factors, and the GCD×LCM relationship — plus multi-number examples and a free calculator.
Read guideHow to Calculate How Much You Need to Retire
Learn nest-egg targets, the 4% rule, contribution growth, inflation, and year-by-year retirement projections — free online calculator.
Read guideHow to Calculate Inflation and Purchasing Power
Learn CPI-based inflation math, convert past dollars to today, project future prices, and adjust salary goals for purchasing power — free online.
Read guideHow to Calculate Loan Payments and Interest
Learn the fixed-rate loan payment formula, amortization, how extra payments cut interest, and how to compare loan terms with a free online calculator.
Read guideHow to Calculate Mean Absolute Deviation
Learn the MAD formula, step-by-step absolute deviations, and when mean absolute deviation is clearer than standard deviation — free tool.
Read guideHow to Calculate Mean, Median, and Mode
Learn arithmetic mean, median, mode, and weighted averages — when each measure fits and how to compute them step by step.
Read guideHow to Calculate Percentage Difference vs Percentage Change
Learn percentage difference vs percentage change formulas, increase and decrease math, and when to use each so two-number comparisons stay honest.
Read guideHow to Calculate Percentage Increase or Decrease
Learn the percentage change formula, signed increase and decrease, reverse calculations, and how change differs from percentage difference.
Read guideHow to Calculate Percentage Off a Sale Price
Learn the percent-off formula, sale price and savings, stacked discounts, and how to apply tax after a markdown with clear examples.
Read guideHow to Calculate Percentages (With Everyday Examples)
Learn four percentage modes: X% of Y, X is what % of Y, percent change, and reverse percentages — with clear formulas, examples, and a free calculator.
Read guideHow to Calculate Permutations and Combinations
Learn nPr vs nCr, when order matters, factorial formulas, and everyday counting examples — with clear steps and a free permutations calculator.
Read guideHow to Calculate Powers, Roots, and Exponents
Compute x^n, nth roots, negative and fractional exponents, and scientific notation — clear rules plus a free power calculator.
Read guideHow to Calculate Probability for Everyday Events
Learn single-event probability, AND/OR rules, conditional probability, and odds vs probability with clear examples — free online.
Read guideHow to Calculate Profit Margin and Markup
Learn gross profit margin vs markup, convert between them, price from cost, and use clear formulas with examples — free online calculator.
Read guideHow to Calculate Sales Tax on a Purchase
Learn sales tax = rate × price, reverse pre-tax from total, state rate overview, and tax-free states — with clear examples and a free tool.
Read guideHow to Calculate Speed, Distance, or Time
Learn the speed-distance-time formula triangle, unit conversions, pace, and how to solve for any missing variable on trips or runs.
Read guideHow to Calculate Square Footage for Rooms and Flooring
Learn room square footage for rectangles and multi-room layouts, flooring waste allowances, and how to convert sq ft to sq m or yards.
Read guideHow to Calculate Standard Deviation and Variance
Learn population vs sample standard deviation, variance formulas, step-by-step calculations, and why spread matters — free online tool.
Read guideHow to Calculate Student Loan Payments
Learn standard student loan payment math, interest, extra payments, and a high-level IDR overview — educational examples with a free calculator.
Read guideHow to Calculate the Area of Common Shapes
Find area for circles, rectangles, triangles, and more with formulas, units, and worked examples — free area calculator guide.
Read guideHow to Calculate the Slope of a Line
Learn rise over run, y = mx + b, parallel and perpendicular slopes, and inclination angle — free slope calculator guide.
Read guideHow to Calculate Tips and Split a Restaurant Bill
Learn 15/18/20% tip math, tax before or after tip, splitting the check, rounding, and service customs — then calculate free online.
Read guideHow to Calculate Variance in Statistics
Learn population vs sample variance, the step-by-step formula, squared deviations, and how variance relates to standard deviation — free tool.
Read guideHow to Calculate What You Need on Your Final Exam
Learn the target-grade formula using current grade and final exam weight so you know the score you need on the final to hit your goal.
Read guideHow to Calculate Whether Refinancing Saves Money
Learn break-even math, monthly savings vs closing costs, rate-and-term vs cash-out refinance, and how to run the numbers before you apply.
Read guideHow to Calculate Your Daily Calorie Needs
Learn BMR with Mifflin-St Jeor, TDEE activity multipliers, deficit and surplus targets, macro basics, and common calorie-counting mistakes — free online.
Read guideHow to Calculate Your GPA on a 4.0 Scale
Learn letter-grade points, credit-hour weighting, semester vs cumulative GPA, target GPA planning, and weighted grades — free online.
Read guideHow to Calculate Your Monthly Mortgage Payment
Learn the mortgage amortization formula, principal vs interest, how term length changes total cost, and how to run the numbers with a free online calculator.
Read guideHow to Check Color Contrast for Accessibility
Learn WCAG color contrast: AA and AAA ratios (4.5:1 and 7:1), large text rules, live previews, and how to fix failing color pairs.
Read guideHow to Check if an A/B Test Is Statistically Significant
Check A/B test significance with conversion rates, uplift, and a 2-proportion z-test overview — plus sample size caveats and a free calculator.
Read guideHow to Check if Two Words Are Anagrams
Learn how anagrams work with letter frequency counts, multi-word phrases, and puzzle tips — plus a free anagram checker tool.
Read guideHow to Check Password Strength and Pick Safer Passwords
Learn password entropy, length vs complexity, crack-time estimates, weak patterns, and client-side strength checks that keep passwords off servers.
Read guideHow to Check Your Screen Resolution and Viewport Size
Learn the difference between screen resolution and browser viewport, how DPR and Retina scaling work, and how to read live display metrics for design.
Read guideHow to Compare Cost of Living Between Cities
Learn city cost indexes, salary equivalents, and housing-to-transport breakdowns so you can compare budgets before you relocate.
Read guideHow to Convert Between Binary, Decimal, and Hex
Convert binary, octal, decimal, and hex with place value, nibble groups, and common CS uses — free multi-base converter with bit views.
Read guideHow to Convert Between Number Bases
Learn binary, octal, decimal, and hex, bases 2–36, and a step-by-step method so you can convert number systems accurately.
Read guideHow to Convert Binary to Text and Back
Learn binary to text conversion with ASCII and UTF-8, spaced binary strings, character breakdowns, and how to encode text back to binary.
Read guideHow to Convert Celsius, Fahrenheit, and Kelvin
Learn °C, °F, and K conversion formulas, cooking vs weather ranges, absolute zero, Rankine basics, and common mistakes — with a free temperature converter.
Read guideHow to Convert Characters to ASCII Codes
Learn how to convert characters to ASCII and Unicode values in decimal, hex, octal, and binary, plus how to read ASCII tables and encoding limits.
Read guideHow to Convert CSV to JSON
Learn CSV headers, delimiters, array-of-objects output, quoted fields, and edge cases so your spreadsheet data becomes clean JSON every time.
Read guideHow to Convert Decimals to Fractions
Learn decimal-to-fraction conversion with place value, GCD simplification, mixed numbers, and repeating decimals — plus clear examples and a free tool.
Read guideHow to Convert Epoch Unix Time to a Readable Date
Learn Unix epoch seconds vs milliseconds, live clocks, ISO/UTC/local output, and how epoch time relates to API timestamps.
Read guideHow to Convert Fractions to Decimals
Learn fraction-to-decimal conversion by division, repeating bars, mixed numbers, and simplify-first tips — with clear examples and a free converter.
Read guideHow to Convert Hex Colors to RGB and HSL
Learn hex, RGB, HSL, and CMYK conversions for web design, live previews, contrast checks, and complementary color palettes.
Read guideHow to Convert JSON to CSV
Learn array-of-objects shape, header detection, nested key flattening, delimiters, and a clean workflow to export JSON into spreadsheet-ready CSV.
Read guideHow to Convert Length and Distance Units
Convert metric and imperial length, distance, area, and volume units with exact factors, worked examples, and a free length converter.
Read guideHow to Convert Markdown to HTML
Learn headings, lists, links, code blocks, and live preview so you can convert Markdown to clean semantic HTML with confidence.
Read guideHow to Convert Numbers to Standard Form
Convert decimals to standard form (a × 10ⁿ), compare scientific and engineering notation, and track sig figs — free converter guide.
Read guideHow to Convert Roman Numerals to Numbers
Learn Roman numeral symbols I V X L C D M, subtractive notation, valid ranges, and step-by-step methods to convert Roman numerals to numbers.
Read guideHow to Convert Salary and Estimate Take-Home Pay
Convert hourly to annual salary, compare gross vs net, estimate FICA and federal tax, and model deductions — free online paycheck math.
Read guideHow to Convert Text Between Cases (camelCase, snake_case, and More)
Convert text to UPPER, lower, Title, camelCase, PascalCase, snake_case, and kebab-case for code, CSS, and copy — with a free converter.
Read guideHow to Convert Time Between Time Zones
Learn UTC offsets, 12/24-hour formats, meeting planning across zones, and how day changes when you convert local times worldwide.
Read guideHow to Convert Units of Length, Weight, and Volume
Learn metric vs imperial length, weight, and volume conversions, precision tips, categories, and common factors with a free unit converter.
Read guideHow to Convert Unix Timestamps to Dates
Learn Unix epoch seconds vs milliseconds, ISO 8601, timezones, and how to convert timestamps when debugging logs and APIs.
Read guideHow to Count Characters, Words, and Bytes in Text
Count characters with and without spaces, words, Unicode and emoji graphemes, and UTF-8 bytes — plus common platform length limits.
Read guideHow to Count Words and Estimate Reading Time
Learn word, character, and sentence counts, reading-time estimates, readability scores, and keyword density so you hit limits with confidence.
Read guideHow to Create a D&D Character Name and Concept
Build a D&D character concept from class fantasy, race and alignment hooks, archetype-fitting names, and party balance — plus a free class-themed name generator.
Read guideHow to Create a QR Code for Links and Wi-Fi
Learn static vs dynamic QR codes, URL and Wi-Fi payloads, colors, PNG/SVG export, and privacy tips for scannable codes that actually work.
Read guideHow to Create a Unique Gamertag (Xbox, PSN, Steam & Discord)
Learn what makes a strong gamertag, platform character limits, and how to generate unique names for Xbox, PlayStation, Steam, and Discord — free and fast.
Read guideHow to Create Custom 2048 Boards Online
Create custom 2048 boards with random, manual, and play modes, grid sizes from 3×3 to 8×8, custom labels, and free PNG export.
Read guideHow to Decode a JWT and Read Its Claims
Learn JWT header, payload, and signature, Base64URL claims, expiration checks, and why decoding is not the same as verification.
Read guideHow to Estimate a Weight Loss Timeline
Learn TDEE, calorie deficits, safe loss rates, and week-by-week projections so you can estimate a realistic weight loss timeline — free tool.
Read guideHow to Estimate Your Take-Home Paycheck
Estimate take-home pay from gross wages: FICA, federal tax brackets, pay frequencies, and 401(k) or health deductions — free online.
Read guideHow to Find Hidden Invisible Characters in Text
Find zero-width spaces, BOM, RTL marks, and other invisible Unicode characters that break paste, length counts, and code — free checker.
Read guideHow to Find the Midpoint Between Two Points
Use the midpoint formula in 2D and 3D, then connect distance, slope, and perpendicular bisectors — free midpoint calculator guide.
Read guideHow to Find the Prime Factorization of a Number
Learn factor trees, prime factorization in exponent form, divisors, and how primes connect to GCD — with a free prime factorization tool.
Read guideHow to Format and Validate JSON
Learn how to pretty-print, minify, and validate JSON, fix syntax errors, use tree views, and debug API payloads with a free formatter.
Read guideHow to Fuse Two Pokémon Into a Custom Hybrid
Learn how to pick parent Pokémon, blend names, combine types, average stats, and share custom fusions with a free online fusion generator.
Read guideHow to Generate a Strong Random Password
Learn length, character sets, entropy, passphrases vs random strings, and safe storage so you can generate passwords you can actually use.
Read guideHow to Generate D&D Character Names by Race
Generate lore-friendly D&D names by race — Elf, Dwarf, Tiefling, Dragonborn, and more — with first/last patterns, NPC banks, and free tools.
Read guideHow to Generate Fake Phone Numbers for Testing
Learn how to create realistic US test phone numbers with valid area codes for forms, QA, and demos — synthetic data only, not for spam or fraud.
Read guideHow to Generate Harmonious Color Palettes
Build harmonious palettes with analogous, complementary, triadic, and monochromatic schemes using HSL — plus a free 5-color generator.
Read guideHow to Generate Lorem Ipsum Placeholder Text
Learn why designers use lorem ipsum, paragraphs vs words, mockup workflows, and HTML output so placeholder text helps layout instead of getting in the way.
Read guideHow to Generate Memorable D&D NPCs
Build memorable D&D NPCs with race, class, alignment, voice, motivation, and quirks — practical DM tips plus a free generator for session prep.
Read guideHow to Generate Narrative D&D Encounters
Build narrative D&D encounters with combat, social, and exploration hooks, complications, and rewards — not just XP math. Free generator.
Read guideHow to Generate Random Dates for Testing and Games
Generate random dates within year ranges for QA test data, games, and mock profiles — with ISO format, day of week, and free tools.
Read guideHow to Generate Random IPv4 and IPv6 Addresses
Learn IPv4 classes, private ranges, IPv6 notation, and testing use cases so you can generate realistic sample IP addresses safely.
Read guideHow to Generate Random MAC Addresses
Learn MAC formats (colon, dash, Cisco), hex digits, and testing use cases so you can generate sample hardware addresses safely.
Read guideHow to Generate Random Numbers Within a Range
Learn min/max ranges, integers vs decimals, bulk generation, and fair use cases so you can pick unbiased random numbers online.
Read guideHow to Generate Random Strings and Tokens
Learn how to generate random strings and tokens: alphanumeric, hex, Base64, length, entropy, and safe use for API keys and test data.
Read guideHow to Generate Random Words for Writing and Games
Learn how to use random word categories for prompts, vocabulary practice, and games so you can break creative blocks with curated word lists.
Read guideHow to Generate Unique Usernames for Any Platform
Generate unique usernames for social, work, and apps — styles, platform norms, availability mindset, and how handles differ from gamertags.
Read guideHow to Make a Perfect Circle in Minecraft
Learn how to build pixel-perfect circles, towers, and domes in Minecraft. Use diameter charts, block counts, and free generator steps — no mods required.
Read guideHow to Measure Reaction Time Online
Learn how visual reaction tests work, typical human millisecond ranges, fair test conditions, and practice tips with a free online reaction timer.
Read guideHow to Measure Typing Speed in WPM
Learn WPM vs CPM, accuracy scoring, timed tests, and practice tips so you can measure typing speed and improve with confidence.
Read guideHow to Project Savings Growth With Compound Interest
Learn how initial deposits, monthly contributions, compounding, and inflation shape savings growth — then project totals free online.
Read guideHow to Roll Random Loot for D&D 5e
Roll D&D 5e loot by rarity tier — Common to Legendary — with magic items, gold, session rewards, and merchant stock tips plus a free generator.
Read guideHow to Round Numbers Correctly
Learn decimal-place rounding, significant figures, floor and ceiling, truncation, and bankers rounding — plus when finance and science need different rules.
Read guideHow to Simplify a Ratio to Lowest Terms
Learn GCD-based ratio simplification for 2-term and 3-term ratios, plus percentages and proportions, so you can reduce any ratio cleanly.
Read guideHow to Solve Quadratic Equations Step by Step
Solve ax² + bx + c = 0 with the quadratic formula, discriminant, roots, and vertex form — free step-by-step quadratic solver guide.
Read guideHow to Test Mouse Buttons, Scroll Wheel, and Tracking
Learn how to check left/right/middle clicks, double-click faults, scroll, and pointer tracking so you can diagnose mouse problems quickly online.
Read guideHow to Test Regular Expressions Online
Learn how to test regex live: flags, capture groups, match highlighting, common patterns, and pitfalls that break JavaScript RegExp.
Read guideHow to Test Your Click Speed in CPS
Learn what CPS means, jitter and kohi click modes, fair testing habits, and how to improve click speed with a free 10-second CPS test.
Read guideHow to Test Your Keyboard for Dead Keys and Ghosting
Learn how to check dead keys, n-key rollover, ghosting, and key codes so you can diagnose keyboard problems before you buy a replacement.
Read guideHow to Test Your Webcam Online
Learn how to check live preview, resolution, permissions, and screenshots so you can fix blurry video, black screens, and wrong cameras before a call.
Read guideHow to Translate Text to Morse Code (And Back)
Learn ITU Morse letters and timing, WPM practice, the full chart, audio playback tips, and how to translate text to Morse and back online.
Read guideHow to Use a Virtual Dice Roller Fairly
Learn fair d6 rolls, multi-dice totals, board-game use cases, and how digital dice randomness compares to physical dice — free online roller.
Read guideHow to Use a Yes or No Generator for Quick Decisions
Learn when a random yes/no answer helps, how it compares to a coin flip, and how session stats work so you can break small ties without overthinking.
Read guideHow to Use Sleep Cycles to Pick a Bedtime
Learn 90-minute sleep cycles, bedtime vs wake-up modes, age-based sleep hours, and sleep debt basics so you wake less groggy — free online.
Read guideHow to Validate a UUID Format and Version
Check UUID/GUID strings against RFC 4122 layout, detect versions 1–7, batch-validate IDs, and know when to generate new UUIDs instead.
Read guideHow to Validate an ads.txt File for IAB Compliance
Learn how ads.txt works, how DIRECT and RESELLER records differ, what domains and IDs must look like, and how to catch common formatting errors before go-live.
Read guideHow to Validate an Email Address Format
Learn RFC-style email syntax, disposable domains, provider detection, plus-aliases, and what format validation can and cannot prove.
Read guideHow URL Encoding Works (Percent Encoding)
Learn percent encoding, encodeURI vs encodeURIComponent, query params, special characters, and UTF-8 so your URLs stay valid and parse correctly.
Read guideHow UUIDs Work and When to Generate Them
Learn UUID v4 structure, collision risk, bulk generation, hyphen and case formats, and how to use UUIDs safely in databases and APIs.
Read guideGuides by category
Calculators
- How Absolute Value Works (And How to Calculate It)
- How Annuity Payments and Present Value Work
- How APY Works and How to Compare Savings Rates
- How Binary Arithmetic Works (Add, Subtract, Multiply)
- How Factorials Work (And How to Calculate n!)
- How Life Expectancy Estimates Are Calculated
- How Linear Regression Finds a Best-Fit Line
- How Long Division Works (Step by Step)
- How Much House Can You Afford?
- How Ovulation Calculators Estimate Fertile Days
- How Roth IRA Growth Works Over Time
- How Simple and Compound Interest Work
- How to Add, Subtract, and Calculate Work Hours
- How to Calculate & Interpret Your BMI
- How to Calculate a Weighted Grade
- How to Calculate a Z-Score
- How to Calculate Aspect Ratios for Images and Video
- How to Calculate CD Interest and Build a CD Ladder
- How to Calculate Days Between Two Dates
- How to Calculate Discounts and Sale Prices
- How to Calculate Electricity Cost for Appliances
- How to Calculate Exact Age From a Date of Birth
- How to Calculate Fuel Cost for a Trip
- How to Calculate GCD and LCM
- How to Calculate How Much You Need to Retire
- How to Calculate Inflation and Purchasing Power
- How to Calculate Loan Payments and Interest
- How to Calculate Mean Absolute Deviation
- How to Calculate Mean, Median, and Mode
- How to Calculate Percentage Difference vs Percentage Change
- How to Calculate Percentage Increase or Decrease
- How to Calculate Percentage Off a Sale Price
- How to Calculate Percentages (With Everyday Examples)
- How to Calculate Permutations and Combinations
- How to Calculate Powers, Roots, and Exponents
- How to Calculate Probability for Everyday Events
- How to Calculate Profit Margin and Markup
- How to Calculate Sales Tax on a Purchase
- How to Calculate Speed, Distance, or Time
- How to Calculate Square Footage for Rooms and Flooring
- How to Calculate Standard Deviation and Variance
- How to Calculate Student Loan Payments
- How to Calculate the Area of Common Shapes
- How to Calculate the Slope of a Line
- How to Calculate Tips and Split a Restaurant Bill
- How to Calculate Variance in Statistics
- How to Calculate Whether Refinancing Saves Money
- How to Calculate Your Daily Calorie Needs
- How to Calculate Your GPA on a 4.0 Scale
- How to Calculate Your Monthly Mortgage Payment
- How to Compare Cost of Living Between Cities
- How to Convert Salary and Estimate Take-Home Pay
- How to Estimate a Weight Loss Timeline
- How to Estimate Your Take-Home Paycheck
- How to Find the Midpoint Between Two Points
- How to Find the Prime Factorization of a Number
- How to Project Savings Growth With Compound Interest
- How to Round Numbers Correctly
- How to Simplify a Ratio to Lowest Terms
- How to Solve Quadratic Equations Step by Step
- How to Use Sleep Cycles to Pick a Bedtime
Converters
- How Base64 Encoding Works (And When to Use It)
- How Scientific Notation Works
- How to Convert Between Binary, Decimal, and Hex
- How to Convert Between Number Bases
- How to Convert Binary to Text and Back
- How to Convert Celsius, Fahrenheit, and Kelvin
- How to Convert Characters to ASCII Codes
- How to Convert CSV to JSON
- How to Convert Decimals to Fractions
- How to Convert Epoch Unix Time to a Readable Date
- How to Convert Fractions to Decimals
- How to Convert Hex Colors to RGB and HSL
- How to Convert JSON to CSV
- How to Convert Length and Distance Units
- How to Convert Markdown to HTML
- How to Convert Numbers to Standard Form
- How to Convert Roman Numerals to Numbers
- How to Convert Text Between Cases (camelCase, snake_case, and More)
- How to Convert Time Between Time Zones
- How to Convert Units of Length, Weight, and Volume
- How to Convert Unix Timestamps to Dates
- How to Decode a JWT and Read Its Claims
- How to Translate Text to Morse Code (And Back)
- How URL Encoding Works (Percent Encoding)
Fun & Random
Testers
Checkers
- How Credit Card Number Validation Works (Luhn)
- How to Check Color Contrast for Accessibility
- How to Check if Two Words Are Anagrams
- How to Check Password Strength and Pick Safer Passwords
- How to Check Your Screen Resolution and Viewport Size
- How to Count Characters, Words, and Bytes in Text
- How to Count Words and Estimate Reading Time
- How to Find Hidden Invisible Characters in Text
- How to Format and Validate JSON
- How to Test Regular Expressions Online
- How to Validate an ads.txt File for IAB Compliance
- How to Validate an Email Address Format
Developer
Utility
- How GUIDs and UUID v4 Identifiers Work
- How IMEI Numbers Work and How Test IMEIs Are Built
- How to Generate Fake Phone Numbers for Testing
- How to Generate Random Dates for Testing and Games
- How to Generate Random IPv4 and IPv6 Addresses
- How to Generate Random MAC Addresses
- How to Generate Random Numbers Within a Range
Generators
Education
Gaming
- How to Build a Balanced D&D 5e Encounter
- How to Build a Dome in Minecraft
- How to Build a Sphere in Minecraft Layer by Layer
- How to Build Minecraft Commands Without Syntax Errors
- How to Create a Unique Gamertag (Xbox, PSN, Steam & Discord)
- How to Create Custom 2048 Boards Online
- How to Fuse Two Pokémon Into a Custom Hybrid
- How to Generate Memorable D&D NPCs
- How to Generate Narrative D&D Encounters
- How to Make a Perfect Circle in Minecraft
- How to Roll Random Loot for D&D 5e
Name Generators
Text & Writing
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