Significant figures indicate the precision of a measurement. Every measured value has a limited number of reliable digits, and calculations should preserve — not falsely improve — this precision. This calculator counts sig figs, rounds to desired precision, and explains which rules apply to each digit.
How to Use
Enter a number to see:
- Sig fig count: How many significant digits
- Digit breakdown: Which digits are significant and why
- Rounding: Round to any number of sig figs
Sig Fig Rules
- All non-zero digits are significant (1-9)
- Zeros between non-zero digits are significant (101 = 3 sig figs)
- Leading zeros are NOT significant (0.0045 = 2 sig figs)
- Trailing zeros after decimal point ARE significant (2.50 = 3 sig figs)
- Trailing zeros in whole numbers are ambiguous (1500 = 2-4 sig figs)
Sig Figs in Calculations
- Multiplication/Division: Result has the fewest sig figs of any operand
- Addition/Subtraction: Result has the fewest decimal places of any operand
Step-by-Step Instructions
- 1Enter a number in the input field.
- 2View the significant figures count and breakdown.
- 3Set a desired number of sig figs for rounding.
- 4View the rounded result.
- 5Check which rules applied to each digit.