Significant Figures Calculator
Count significant figures in a number and round to a chosen number of sig figs.
Best for: Use it in chemistry, physics and engineering to report measurements to the correct precision, or to check homework.
Purpose: Count significant figures in a number and round to a chosen number of sig figs.
Input
Result
ExactSignificant figures
4
What to do next
Next: Percent Error CalculatorMore about this result
- Type
- Exact Formula
- Method
- Standard mathematical formula
- Confidence
- High
A precise, deterministic calculation - the same inputs always give exactly this result.
The count tells you the precision a number claims. Rounding to fewer sig figs reflects the precision of your least-precise measurement - the usual rule when multiplying or dividing.
- Watch units and rounding — they change the answer.
- Order of operations matters; group terms carefully.
- Re-run with different inputs to sanity-check the result.
The same data can tell different stories - which average you use changes the answer.
How it's calculated & sources
Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.
How it works
Non-zero digits always count; leading zeros never do; trailing zeros count only after a decimal point. Then round to the requested number of significant figures.
Example
0.004560 has 4 significant figures (4, 5, 6, 0). Rounded to 2 sig figs = 0.0046.
Frequently asked questions
Are trailing zeros significant?+
Only when a decimal point is present. 1500 has 2 significant figures; 1500. and 1500.0 have 4. Leading zeros (as in 0.0025) are never significant.
Sig figs vs decimal places?+
Decimal places count digits after the point; significant figures count meaningful digits from the first non-zero one. 0.004560 has 6 decimal places but 4 significant figures.
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