DailyCalc

Significant Figures Calculator

Count significant figures and round any number to n sig figs.

Type it exactly as measured, keeping trailing zeros: 2.50, 1300., 1.2e3.

Try an example

Significant figures

5

0.0052070 has 5 significant figures: 5, 2, 0, 7, 0.

Leading zeros
3 (not significant)
Non-zero digits
3
Zeros between digits
1 (significant)
Trailing zeros
1 (significant: after a decimal point)
Scientific notation
5.2070 × 10⁻³
Rounded to 3 significant figures (round half to even)
0.00521

Fix the highlighted field to update the result.

How to use

  1. Type the number exactly as measured, keeping any trailing zeros: 2.50, 1300. or 1.30e3.
  2. Read how many significant figures it has and why each zero counts or not.
  3. To round, choose how many significant figures to keep and the rule for a dropped 5.

How counting significant figures works

  • Non-zero digits always count.
  • Captive zeros, between non-zero digits, always count: 70.607 has five.
  • Leading zeros never count; they only place the decimal point: 0.00832407 has six.
  • Trailing zeros count only when there is a decimal point: 55.0 has three.
  • A whole number like 1300 is ambiguous: two, three or four. Scientific notation removes the doubt.

To round to n significant figures, count n digits from the first non-zero digit and look at the next one. If the dropped digit is exactly 5 with nothing after it, OpenStax and NIST round to the even digit.

Examples

Number Significant figures Why
0.00832407 6 Leading zeros don’t count
70.607 5 Captive zeros count
55.0 3 Trailing zero after a point
1300 2 (ambiguous) No decimal point
1.300 × 10³ 4 Scientific notation
15,450.0 6 Trailing zeros after a point
  • 18.3384 to 3 significant figures: the next digit is 3, so 18.3.
  • 0.028675 to 3 significant figures: the next digit is 7, so 0.0287.
  • 92.85 to 3 significant figures: the dropped 5 is a tie, so round to even: 92.8. Rounding 5s up gives 92.9.
  • 2648 to 2 significant figures: 2,600, written 2.6 × 10³ to show that only two digits are significant.
Calculations, exact numbers and the trailing point

When multiplying or dividing, keep the fewest significant figures of the inputs: 0.6238 × 6.6 = 4.11708, reported as 4.1. When adding or subtracting, keep the fewest decimal places.

Exact numbers, such as counted items or 1 foot = 12 inches, have unlimited significant figures.

Some classes write “1300.” with a trailing point to mean four significant figures. The calculator accepts it, but scientific notation is clearer.

To write the result in scientific notation, use the scientific notation calculator.

Frequently asked questions

How many significant figures does 0.00832407 have?

Six. Leading zeros only show where the decimal point sits, so counting starts at the 8: 8, 3, 2, 4, 0 and 7. The captive zero counts.

Are trailing zeros significant?

Only when the number has a decimal point. 55.0 has three, but 1300 is ambiguous (two, three or four). Writing 1.30 × 10³ makes it clear: three.

How do I round to 3 significant figures?

Count three digits from the first non-zero digit, then look at the next digit to decide. 18.3384 becomes 18.3, and 0.028675 becomes 0.0287.

What if the dropped digit is exactly 5?

OpenStax and NIST round to the even digit, so 92.85 becomes 92.8 at three sig figs. Many classes round 5 up instead (92.9), so you can pick either rule.

Do exact numbers have significant figures?

Exact numbers have unlimited significant figures. Counted items and defined values, such as 1 foot = 12 inches, never limit the precision of a calculated answer.

How many sig figs should a product have?

As many as the input with the fewest. 0.6238 × 6.6 = 4.11708, which is reported as 4.1 because 6.6 has only two significant figures.