Significant Figures Calculator

Count significant figures in any number and round a value to a specified number of significant figures.

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Enter values Enter a number to count its significant figures.

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Significant figures calculator: count and round sig figs

A significant figures calculator counts the number of significant figures in any number and rounds a value to a specified number of significant figures. Significant figures indicate the precision of a measurement: the more significant figures, the more precise the value. Understanding sig figs is essential in science, engineering, and any field where measurement uncertainty matters.

Rules for counting significant figures

All non-zero digits are significant. Zeros between non-zero digits are significant (e.g., 1002 has four sig figs). Leading zeros are not significant (0.0045 has two sig figs). Trailing zeros after a decimal point are significant (2.50 has three sig figs). Trailing zeros in a whole number without a decimal point are ambiguous.

When performing calculations, the result should be rounded to match the precision of the least precise input. For multiplication and division, match the fewest significant figures. For addition and subtraction, match the fewest decimal places.

Why significant figures matter

Reporting too many digits implies a level of precision that the measurement does not support. If a bathroom scale reads to the nearest 0.1 kg, reporting your weight as 72.345 kg is misleading. The correct report is 72.3 kg.

In chain calculations, rounding too early can compound errors. A common practice is to keep one or two extra significant figures during intermediate steps and round only the final answer to the appropriate number of sig figs.

Frequently asked questions

How many significant figures does the number 0.00320 have?

Three. The leading zeros (0.00) are not significant. The digits 3, 2, and the trailing 0 are all significant because the trailing zero after a decimal indicates measured precision.

 Should I round intermediate steps in a calculation?

Keep at least one extra significant figure during intermediate steps to avoid compounding rounding errors. Round only the final result to the appropriate number of significant figures.

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