Significant figures calculator

How many significant figures a number has, and the number rounded to as many as you need.

Formula Maths

Significant figures

Scientific notation: 4.560 × 10⁻³

How it works

All non-zero digits are significant. Zeros between non-zero digits are significant. Leading zeros, such as those in 0.0045, only place the decimal point and are not significant.

Trailing zeros are significant when the number has a decimal point: 2.50 has three. In a whole number with no decimal point, such as 1200, they may or may not be, so the calculator gives the minimum and the range.

Formula

non-zero digits: significant
zeros between them: significant
leading zeros: not significant
trailing zeros: significant only with a decimal point

Worked example

0.004560 has 4 significant figures (4, 5, 6 and the final 0) and is 4.560 × 10⁻³. 1200 has 2 to 4, while 1200. has 4.

Questions people ask

Are trailing zeros significant?

After a decimal point, yes: 3.00 has three. In a whole number like 500 it is unclear unless written as 5.00 × 10².

How many significant figures should an answer have?

For multiplication and division, use the smallest number of significant figures among the inputs.

Are exact numbers limited by significant figures?

No. Counted or defined values, such as 12 eggs or 100 cm in a metre, have unlimited significant figures.