Aspect Ratio Calculator

Calculate & convert aspect ratios

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About Aspect Ratio Calculator

An aspect ratio calculator that finds the aspect ratio from any width and height, calculates missing dimensions given a ratio, and scales proportionally. Supports common presets (16:9, 4:3, 21:9, 1:1) and custom ratios. Shows GCD-reduced ratios, pixel counts, and common use cases for each ratio. Essential for video editors, photographers, web designers, and UI developers working with responsive layouts.

Aspect Ratio Calculator Features

  • Ratio detection
  • Dimension calculator
  • Common presets
  • Proportional scaling
  • Pixel count
Aspect ratio is the proportional relationship between width and height. A 16:9 display is 16 units wide for every 9 units tall. Understanding aspect ratios is crucial for video production (avoiding letterboxing), photography (print sizes), web design (responsive images), and UI layouts.

How to Use

Enter any two values:

  • Width + Height: Detects the aspect ratio
  • Width + Ratio: Calculates the height
  • Height + Ratio: Calculates the width

Common Aspect Ratios

  • 16:9 — HD/4K video, modern monitors
  • 4:3 — Classic TV, iPad
  • 21:9 — Ultrawide monitors, cinema
  • 1:1 — Instagram square
  • 9:16 — Mobile vertical video (TikTok, Reels)

The Math

Aspect ratio = GCD-reduced Width:Height. For 1920×1080: GCD(1920,1080) = 120, so 1920/120 : 1080/120 = 16:9.

Step-by-Step Instructions

  1. 1Enter width and height in pixels.
  2. 2View the detected aspect ratio.
  3. 3Or select a preset ratio and one dimension.
  4. 4See the calculated missing dimension.
  5. 5Check pixel count and common uses.

Aspect Ratio Calculator — Frequently Asked Questions

What aspect ratio is 1920×1080?+

16:9 — the standard for Full HD. GCD(1920,1080)=120, giving 16:9.

What's the best aspect ratio for YouTube?+

16:9 (1920×1080 or 3840×2160). YouTube's player is 16:9, so other ratios get letterboxed or pillarboxed.

How do I maintain aspect ratio when resizing?+

Multiply both dimensions by the same factor. Or calculate: new_height = new_width × (original_height / original_width).

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