Significant Figures Calculator
Count significant figures or round a number to a chosen number of significant figures. Built for science, chemistry, physics, and lab-report calculations.
What significant figures mean
Significant figures show the meaningful digits in a measured value. OpenStax defines significant figures as measured digits including the uncertain last digit in its measurement uncertainty, accuracy, and precision section. This calculator counts significant figures and rounds numbers to a chosen number of significant figures.
Significant figure rules
| Rule | Example |
|---|---|
| Nonzero digits are significant | 347 has 3 sig figs |
| Leading zeros are not significant | 0.0045 has 2 sig figs |
| Zeros between nonzero digits are significant | 1007 has 4 sig figs |
| Trailing zeros after a decimal are significant | 2.300 has 4 sig figs |
Adding, subtracting, multiplying, and dividing
When multiplying or dividing measured values, the final answer usually keeps the same number of significant figures as the least precise factor. When adding or subtracting, the final answer is rounded to the least precise decimal place. OpenStax gives additional computation rules in its essential mathematics appendix.
Common questions
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They are the meaningful digits in a measured number, including the estimated last digit.
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No. Leading zeros only locate the decimal point.
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Trailing zeros after a decimal are significant. Trailing zeros in a whole number without a decimal can be ambiguous.
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There are 3 significant figures: 4, 5, and the final 0.
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It is ambiguous unless written with a decimal or scientific notation.
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They prevent calculated answers from looking more precise than the measurements used.
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Usually no. Keep extra guard digits and round the final answer.
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Yes. Scientific notation removes ambiguity about trailing zeros.