Significant Figures Calculator
Enter a number and how many significant figures to keep.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- Find the first non-zero digit
- Keep the number of digits you chose and round the last one
- Scientific notation shows the same digits as a × 10ⁿ
For rounding to a place value instead, use the rounding calculator. For writing very large or small numbers, see the scientific notation calculator.
Worked example
123,456 to 3 significant figures:
- Rounded = 123,000
- Scientific = 1.23 × 10⁵
Why your number may differ
Trailing zeros after a decimal point can count as significant in a lab report. This calculator shows the plain rounded number, without padding zeros.
Frequently asked questions
What are significant figures?
The digits in a number that carry meaning, starting from the first non-zero digit. 0.00123 has three significant figures.
How do I round to significant figures?
Keep the first n digits starting from the first non-zero digit, and round the last one using the digit that follows.
Why is 1.5 shown without extra zeros?
The result drops trailing zeros. 1.5 to 5 s.f. is 1.5000 in a lab report, but the number itself is just 1.5.