Significant Figures Calculator
Count the significant figures in a number and round it to any number of sig figs you need. This free online math calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
Significant figures are the digits in a number that carry meaning about its precision. The rules: all non-zero digits count; zeros between non-zero digits count; leading zeros never count; and trailing zeros count only when a decimal point is present. So 0.004560 has four significant figures (4, 5, 6, and the trailing 0).
To round to n significant figures, the calculator uses JavaScript's precision formatting and also expresses the number in scientific notation, where the count of significant figures is always unambiguous.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Number: 0.004560
- Round to how many significant figures?: 3
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
Tips & Considerations
Trailing zeros in a whole number with no decimal point are ambiguous — "1500" could have two, three, or four significant figures. Scientific notation (1.50 × 10³) removes the ambiguity, which is why it is the preferred form in science.
Frequently Asked Questions
Do leading zeros count as significant figures?
No. Leading zeros only place the decimal point and never count. In 0.0042 the two leading zeros are not significant, so the number has two significant figures.
When do trailing zeros count?
Trailing zeros are significant when the number contains a decimal point. 45.60 has four significant figures, but 4560 without a decimal point is ambiguous and is best written in scientific notation.
What does the Significant Figures Calculator compute?
The Significant Figures Calculator takes 2 input values and returns 3 results. Count the number of significant figures in a value and round any number to a chosen number of significant figures, with scientific-notation output.
Is my data sent to a server?
No. The Significant Figures Calculator runs entirely in your browser using static JavaScript. Your inputs are never transmitted to CalculatorHive or any third party, and nothing is stored after you close the page.