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Significant Figures Calculator

Count the significant figures in a number and round it to any number of sig figs, with scientific notation. Follows the standard sig fig rules. Free.

Significant figures
4
Rounded to 2
0.0046
In scientific notation
4.6 × 10^-3

The rules for significant figures

Significant figures are the digits in a number that carry meaning about its precision. Non-zero digits always count. Zeros between them count. Leading zeros never count: 0.004560 has 4 significant figures (4, 5, 6 and the final 0). Trailing zeros count only after a decimal point, so 1200 has 2 but 1200. and 1200.0 have 4 and 5. Rounding to 2 significant figures turns 0.004560 into 0.0046, or 4.6 × 10⁻³.

How to use it

  1. 1

    Enter a number

    Type it exactly as written, with any trailing zeros.

  2. 2

    Choose how many sig figs

    To round to.

  3. 3

    Read the result

    The count, the rounded number and scientific notation.

Frequently asked questions

Do trailing zeros count?

Only if there's a decimal point. 2.50 has 3 significant figures; 250 has 2.

Do leading zeros count?

No. 0.0071 has 2 significant figures.

How many sig figs should an answer have?

For multiplying and dividing, as many as the least precise number in the calculation.

Is anything stored?

No. The calculation runs in your browser.

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