Round to significant figures
Useful for physics and chemistry students reporting results to the precision of the measurement, keeping meaningful zeros such as 2.50.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter number and significant figures.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Count digits from the first non-zero digit and keep n of them. If the next digit is 5 or more, add one to the last kept digit, then replace the rest with zeros.
Example
Inputs: Number = 0.0045678, Significant figures = 3. Result: Rounded: 0.00457.
0.0045678
0.00457
Limits and caveats
- Ties (a 5 followed by zeros) round away from zero; some references round to even instead.
- A plain result such as 120000 hides how many figures are significant, so rely on the scientific form.
Questions about this tool
How do I round 0.0045678 to 3 significant figures?
Leading zeros do not count, so the significant digits are 4, 5 and 6. The next digit is 7, so the answer is 0.00457.
Why does 9.996 become 10.0?
Rounding carries it up to 10, and three significant figures need the trailing zero, so it is written 10.0.
What is the difference between significant figures and decimal places?
Significant figures count from the first non-zero digit. Decimal places count only digits after the point.