Significant Figures Counter
Count the significant figures in any number and round it to a chosen number of sig figs.
Significant figures
4
Leading zeros are not significant. Trailing zeros are significant because there is a decimal point. Zeros between non-zero digits are significant. All non-zero digits are significant.
Rounded to 2 sig figs
0.0045
Type any number to see how many significant figures it has and why, based on standard rounding rules. You can also round the number to a specific number of significant figures — all processed locally in your browser.
How to use
- Enter a number (decimals and scientific notation are supported).
- See the significant figure count and the rule explanation.
- Choose how many significant figures to round to.
Frequently asked questions
- Are trailing zeros significant?
- Trailing zeros are significant only if the number has a decimal point, e.g. 1500 has 2 sig figs but 1500.0 has 5.
- Are leading zeros significant?
- No, leading zeros (e.g. in 0.0045) are never significant — they just indicate the decimal position.
- Does the tool support scientific notation?
- Yes, entering a value like 4.50e3 counts significant figures from the mantissa (4.50).