Significant figures calculator
Count significant figures, or round a number to a set number of significant figures or decimal places.
A clear answer. Here’s how.
Counts follow the standard rules: non-zero digits and zeros between them are significant, leading zeros are not, and trailing zeros count only if the number has a decimal point or is in scientific notation. Rounding works on the exact decimal digits typed, so there are no binary floating-point surprises. A tie (exactly half) rounds away from zero or to the even digit, as chosen. Whole numbers ending in zeros are ambiguous, so use scientific notation to show intent.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Number
- 0.00456780
- Task
- Round to significant figures
- Figures or decimal places for rounding
- 3
- Ties
- Round half away from zero (school rule)
Example result
- Rounded value
- 0.00457
- Scientific notation
- 4.57 × 10^-3
- Significant figures kept
- 3
- Original has
- 6 significant figures
Ties round away from zero. Rounding uses the decimal digits you typed, not binary floating point, so 2.675 rounds as written. If the rounded whole number ends in zeros they may not be significant; use the scientific form to be unambiguous.