Significant figures tell you how precise a measurement really is.
About this calculator
Significant figures tell you how precise a measurement really is. In 0.004560, four digits matter — the leading zeros do not count, but the trailing zero after the decimal does because it shows the balance was read to that place.
Enter any number and this calculator counts its significant figures, then rounds to the count you choose. That pair of steps is what lab reports and board exam answers expect before you plug results into formulas.
Use it after taking readings from a vernier, burette, or digital scale. Pair with the [[rounding]] calculator for fixed decimal places, the [[percentage-error]] calculator to compare measured vs expected values, and the [[scientific-notation]] calculator when values span many orders of magnitude.
Common uses
- Count sig figs in chemistry lab measurements before reporting
- Round calculator output to match instrument precision
- Check board exam rounding rules on homework
- Standardise results before percent error calculations
Frequently asked questions
How many significant figures does 0.004560 have?
Four. Leading zeros before the first 4 are not significant. The digits 4, 5, 6, and the final 0 after the decimal all count.
Are trailing zeros in 1200 significant?
Without a decimal point, trailing zeros in 1200 are ambiguous — often treated as two sig figs. Writing 1200. or 1.200 × 10³ makes the intent clear.
How do you round 12.345 to 3 significant figures?
The fourth digit is 4, so you keep 12.3. If the next digit were 5 or higher, 12.3 would become 12.4.
Do exact counts like 5 students have unlimited sig figs?
Exact integers from counting have unlimited significant figures. Converted measurements — like 5.0 g from a scale — follow normal sig fig rules.