Significant Figures Calculator
Free significant figures calculator: count the significant figures in a number and round it to any number of significant figures, with the rules.
What it does
Significant figures are the digits of a number that carry meaning about its precision. Nonzero digits always count; zeros between them count; leading zeros never count; and trailing zeros count only when there is a decimal point. This calculator counts the significant figures of a number and rounds it to the number of figures you choose, in decimal and in scientific notation.
How to use it
- Type the number exactly as it was measured or given, with its zeros.
- See how many significant figures it has.
- Type how many figures you want to round to.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
What are the rules for counting significant figures?
Count every nonzero digit and the zeros between them (1.05 has 3). Leading zeros do not count (0.0045 has 2). Trailing zeros count after a decimal point (4.500 has 4) but not in a whole number without one (4500 has 2).
How do I round to significant figures?
Keep the chosen number of figures from the first nonzero digit and look at the next one: 5 or more rounds up. 0.0045678 to 2 figures is 0.0046, and 123,456 to 3 figures is 123,000.
How many figures should a result have?
When multiplying or dividing, use as many significant figures as the least precise value. When adding or subtracting, round to the fewest decimal places among the values.
Are exact numbers limited by significant figures?
No. Counted numbers (12 students) and defined values (1 m = 100 cm) are exact and have unlimited significant figures, so they never limit the precision of a result.
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