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Count significant figures in any number and round to a specified number of sig figs. Includes rules reference for leading zeros, trailing zeros, and decimals.
Significant figures (sig figs) are the digits in a number that carry meaning contributing to its measurement precision, following specific rules for leading zeros, trailing zeros, and decimal points.
Significant Figures
3
Rounded
0.0045
| Number | Sig Figs | Rule |
|---|---|---|
| 1234 | 4 | All non-zero |
| 1020 | 3 | Trailing zero, no decimal |
| 0.0056 | 2 | Leading zeros not sig |
| 100.0 | 4 | Trailing zero with decimal |
| 0.00300 | 3 | Trailing zeros after decimal |
| 5.0 × 10³ | 2 | Scientific notation |
Formula
Rules: Non-zero digits are always significant; zeros between them are significant; leading zeros are not; trailing zeros after a decimal are significantSig Fig = A digit that contributes to the precision of a measurement
Leading zero = Zero(s) before the first non-zero digit (not significant)
Trailing zero = Zero(s) after the last non-zero digit (significant only with decimal)
Worked Example
Count sig figs in 0.004050
Did you know? The concept of significant figures became formalized in the 19th century as precision measurement became critical in physics and chemistry, particularly after the adoption of the metric system (source: NIST).
Sources
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