Maths / Measurement
Significant Figures Calculator
Count the significant figures in a number and round a number to any number of significant figures, with the rules for zeros explained.
Significant Figures Calculator: Significant figures are the digits that carry meaning about a measurement's precision. Non-zero digits always count; zeros between them count; leading zeros, as in 0.0045, never count; trailing zeros count only when there is a decimal point, as in 4.50. A whole number like 1200 is ambiguous, with 2 to 4 significant figures, unless written as 1200. or in scientific notation. Rounding keeps the chosen number of digits, keeping trailing zeros that are significant. Runs 100% locally in your browser with zero server file uploads.
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Non-zero digits always count; zeros between them count; leading zeros never count; trailing zeros count only after a decimal point.
Rounding in calculations
Keep extra digits during a calculation and round only the final answer; rounding each step adds error. For multiplication and division, give the answer to as many significant figures as the least precise value used.
To show significant trailing zeros clearly, write the number in scientific notation.
Examples
0.00450 has 3 significant figures; 1005 has 4; 3.0 has 2; 100 has 1, 2, or 3, depending on how precisely it was measured; 1.00 × 10² has 3.
How to use it
- Type the number as written, keeping its zeros, such as 0.004560 or 1200.
- Read how many significant figures it has.
- Choose how many to round to, and read the rounded number and its scientific form.
Privacy & limitations
The calculation runs in your browser.
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Frequently asked questions
How many significant figures does 0.0500 have?
Three: the leading zeros do not count, and the two trailing zeros after the 5 do, because there is a decimal point.
How many significant figures should an answer have?
When multiplying or dividing, as many as the least precise measurement; when adding or subtracting, round to the fewest decimal places.
Do exact numbers limit significant figures?
No: counted numbers and defined constants, such as 12 eggs or 100 cm in a metre, have unlimited significant figures.
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