Significant Figures Calculator
Round a number to a set number of significant figures, and count the sig figs in any value.
How to use it
- Enter a number The value to round or analyse.
- Choose the sig figs How many significant figures to keep.
- Read both results The rounded value and the input's sig-fig count.
Examples
| 3.14159 to 3 | 3.14 |
|---|---|
| sig figs of 100.0 | 4 |
About this tool
Significant figures express how precisely a value is known, and getting them right matters throughout science and engineering. This tool rounds any number to the number of significant figures you choose, and separately counts the significant figures already present in a value.
The rules around zeros trip many people up — leading zeros never count, trailing zeros after a decimal do — and this calculator applies them consistently. Everything is computed in your browser.
Frequently asked questions
Which digits are significant?
All non-zero digits count, zeros between them count, and trailing zeros after a decimal point count. Leading zeros never count.
How are trailing zeros in whole numbers handled?
They're treated as ambiguous and not significant, so 1200 counts as two significant figures unless written with a decimal point.
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Updated June 14, 2026