Sig Fig Calculator

Count the significant figures in a number, or round a value to a chosen number of significant figures. Calculates in your browser.

Type the number as written, trailing zeros after a decimal point count.

Significant figures

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Rounded value-

Show the math

Significant figures are the digits that carry real precision:

leading zeros never count · trailing zeros count only after a decimal point

Non-zero digits always count, as do zeros between them. A bare whole number's trailing zeros are ambiguous and are not counted. All math runs locally in your browser.

What this does

The sig fig calculator counts the significant figures in a number and rounds a value to a chosen number of significant figures, the standard way to report precision in science and engineering.

How to use it

  1. Type a number (decimals and scientific notation are fine).
  2. Read how many significant figures it has.
  3. Enter a target count to round the value.

How it works

All non-zero digits are significant. Leading zeros never count; trailing zeros count only when a decimal point is present. A bare integer’s trailing zeros are treated as ambiguous and are not counted.

Understanding your result

Significant figures show how precisely a value is known, so a measured result should carry no more of them than the least precise input. Watch the trailing-zero rule: "1200" reads as two significant figures, but "1200." or "1.200 × 10³" makes all four explicit, which is why scientific notation removes the ambiguity.

Example

0.00120 has three significant figures; rounding 123456 to three gives 123000.

Sources & methodology

Last updated .

Frequently asked questions

Which digits are significant?

All non-zero digits count. Leading zeros never do. Trailing zeros count only when there is a decimal point, so 0.00120 has three significant figures.

Why is 1200 ambiguous?

Without a decimal point, the trailing zeros in a whole number could be placeholders or measured digits. Write 1200. or 1.2 × 10³ to make the precision explicit.

How does rounding to significant figures work?

The value is rounded so it keeps exactly the number of significant figures you ask for, rounding 123456 to three significant figures gives 123000.

Is my data stored?

No. Everything is calculated locally in your browser.