Significant Figures Calculator
Count the significant figures in a number and optionally round to a specified number of sig figs.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Enter any number as text (to preserve trailing zeros) and the calculator counts its significant figures. Optionally, specify a number of sig figs to round to.
- Enter a number. Type the number exactly as you have it, including any trailing zeros. The input field is text-based to preserve zeros that a numeric field would strip.
- Round (optional). Enter a number in the "Round to sig figs" field to see the number rounded to that many significant figures.
- Read the result. The sig fig count appears along with the rules that were applied (leading zeros, trailing zeros, decimal point significance).
Significant figures indicate the precision of a measurement. More sig figs means greater precision. The rules can be tricky, especially around leading and trailing zeros, and this calculator applies them automatically.
About Significant Figures
Significant figures (sig figs) communicate how precise a measurement is. The rules are: all non-zero digits are significant; zeros between non-zero digits are significant; leading zeros are never significant; trailing zeros after a decimal point are significant; trailing zeros without a decimal point are ambiguous.
In scientific calculations, the result should not have more sig figs than the least precise measurement used. For multiplication and division, the result gets the same number of sig figs as the input with the fewest. For addition and subtraction, the result gets the same number of decimal places as the input with the fewest.
Frequently Asked Questions
What are the rules for significant figures?
Non-zero digits are always significant. Zeros between non-zero digits are significant. Leading zeros (before the first non-zero digit) are not significant. Trailing zeros after a decimal point are significant. Trailing zeros without a decimal point are ambiguous.
How many sig figs does 0.00340 have?
Three significant figures: 3, 4, and the trailing 0. The leading zeros (0.00) are not significant. The trailing zero after the 4 is significant because it comes after the decimal point.
How do you round to a certain number of significant figures?
Count from the first non-zero digit to the desired number of sig figs, then round the rest. For example, 0.004567 rounded to 2 sig figs is 0.0046. The leading zeros do not count toward the sig fig total.