How to Use the Significant Figures Calculator
A value from an experiment or measurement is only as trustworthy as the precision of the tool that produced it, and significant figures are how we express exactly how precise that value is. The rules sound simple at first, but knowing when a leading or trailing zero counts and when it doesn't trips up a lot of students and researchers writing up lab reports.
Enter a measurement and this tool automatically counts its significant figures according to standard rules, then shows the correctly rounded value once you specify how many digits you want. This helps prevent accidentally adding or dropping precision when you transfer a result into a slide deck or report.
Significant Figure Rules
- All non-zero digits are significant
- Zeros sandwiched between non-zero digits are significant
- Leading zeros before the first non-zero digit (like the 0 in 0.005) are never significant
- If there's a decimal point, trailing zeros are significant (e.g., 2.50 → 3 sig figs)
For example, in 0.00230, the three leading zeros don't count, but the 2, the 3, and the trailing zero kept to show precision all count — 3 significant figures total. On the other hand, a number like 1204.50 has a non-zero digit before the decimal, so every digit after it counts too, giving 6 significant figures.
Frequently Asked Questions
0.00230 has 3 significant figures. The leading zeros aren't significant, but the 2, the 3, and the trailing zero after the decimal point are, since it was kept to show precision.
Trailing zeros in a whole number without a decimal point are ambiguous. 1200 is often treated as having 2 significant figures by convention; to be unambiguous, use scientific notation like 1.200×10³.