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Sig Fig Calculator

Count the significant figures in a number and round it to any number of sig figs. Type the number exactly as it is written — trailing zeros and the decimal point matter — and the calculator shows which digits count, the rounded value and its scientific notation.

Quick examples

Type it exactly as written — trailing zeros after a decimal point count.

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Significant figures4
The significant digits
4560
Rounded
0.0046
Rounded, in scientific notation
4.6 × 10⁻³

Saved setups

Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.

    Your recent calculations

    Results you calculate here are kept on this device so you can come back to them.

      Formula

      Non-zero digits are always significant
      Zeros between non-zero digits are significant: 1002 has 4
      Leading zeros are never significant: 0.0045 has 2
      Trailing zeros are significant only when the number has a decimal point: 45.00 has 4, 4500 has 2

      How to use it

      1. Type the number as written, including any trailing zeros.
      2. Read how many significant figures it has and which digits they are.
      3. Enter the number of significant figures you want to round to.
      4. Use the scientific-notation form when the rounded number would otherwise be ambiguous.

      Worked examples

      0.004560 has four significant figures; rounded to two

      Significant figures
      4
      The significant digits
      4560
      Rounded
      0.0046
      Rounded, in scientific notation
      4.6 × 10⁻³

      12,345 rounded to three significant figures

      Significant figures
      5
      Rounded
      12300
      Rounded, in scientific notation
      1.23 × 10⁴

      1200 with no decimal point

      Significant figures
      2
      The significant digits
      12
      Rounded, in scientific notation
      1.20 × 10³

      9.996 rounded to three significant figures

      Significant figures
      4
      Rounded
      10.0
      Rounded, in scientific notation
      1.00 × 10¹

      The ambiguous case

      A whole number ending in zeros, like 1200, does not say whether those zeros were measured. This calculator follows the usual textbook convention and counts 2. To show more, write a decimal point (1200. has 4) or use scientific notation (1.20 × 10³ has 3).

      Sig figs in calculations

      Multiplying or dividing: the answer keeps as many significant figures as the input with the fewest. 4.56 × 1.4 = 6.384, reported as 6.4.

      Adding or subtracting: the answer keeps as many decimal places as the input with the fewest. 12.11 + 18.0 + 1.013 = 31.123, reported as 31.1.

      Counted quantities and defined conversions (12 inches in a foot) are exact and never limit the result.

      Questions people ask

      How many significant figures are in 0.004560?

      Four: 4, 5, 6 and the final 0. The leading zeros only place the decimal point.

      How many significant figures does 1200 have?

      Two as written. Written as 1200. it has four, and as 1.20 × 10³ it has three.

      What is 12,345 rounded to three significant figures?

      12,300, or 1.23 × 10⁴.

      How many significant figures are in 100.0?

      Four. The decimal point makes all the zeros significant.

      Related calculators

      Rounding CalculatorRound to any place value — nearest ten, whole number, tenth, hundredth…Scientific Notation ConverterConvert numbers to and from scientific, E and engineering notation.Percent Error CalculatorHow far a measured value is from the true value, in percent.Standard Deviation CalculatorSample and population standard deviation, side by side.