Toolstia / Significant figures calculator
Significant figures calculator
Type a number to see how many significant figures it has, and round it to the number of significant figures you need. The rules for leading, trailing and captive zeros are applied for you.
Leading zeros never count. Zeros between digits always count. Trailing zeros count when the number has a decimal point (100.0 has four), and are ambiguous without one (1200 is treated as two).
How it works
- Enter the number as it was measured.
- Read the count of significant figures.
- Enter how many figures to keep and read the rounded value.
The counting rules
All non-zero digits count. Zeros between non-zero digits count. Leading zeros never count. Trailing zeros count only when the number has a decimal point.
Examples
0.00120 has 3 significant figures, 100.0 has 4 and 1200 is treated as 2.
Rounding
Rounding to n significant figures keeps the first n meaningful digits and rounds the rest, for example 123456 to 3 figures is 123000 and 0.0012345 to 3 figures is 0.00123.
Why they matter
In measurement, the number of significant figures shows how precise a value is. Results should not claim more precision than the inputs.
Questions
Is 1200 two, three or four figures?
Without a decimal point it is ambiguous. The tool counts it as two. Write 1200. or 1.200e3 to show four.
Does it accept E notation?
Yes, for example 1.20e3.
Is anything uploaded?
No. Your input stays in your browser and is never sent anywhere.