Significant Figures Calculator
Count the significant figures in any number, including tricky zeros, and round it to the number of sig figs you need, in normal and scientific notation.
Type it exactly as written, keeping any zeros. Scientific notation works too: 4.560e-3.
Significant figures
4
- Rounded to 2 significant figures
- 0.0046
- In scientific notation
- 4.6 × 10⁻³
0.004560 has 4 significant figures. To 2, it is 0.0046.
How it's worked out
- Leading zeros
zeros before the first non-zero digit only hold the placenot significant - Zeros between digits
such as the 0 in 405significant - Trailing zeros
after a decimal pointsignificant - Round to 2
keep 2 significant digits, round the next one0.0046
The rules with examples
| Number | Significant figures | Why |
|---|---|---|
| 405 | 3 | zeros between digits count |
| 0.0052 | 2 | leading zeros don't count |
| 5.200 | 4 | trailing zeros after a point count |
| 5200 | 2 (up to 4) | trailing zeros without a point are unclear |
| 5200. | 4 | the point shows the zeros count |
| 5.20 × 10³ | 3 | every digit in the mantissa counts |
The rules
Non-zero digits always count. Zeros between them count. Leading zeros never count. Trailing zeros count after a decimal point, and are ambiguous in a whole number with no point.
Examples
0.004560 has 4 · 1200. has 4 · 1200 has 2 to 4 · 4.560 × 10⁻³ has 4 · 100.0 has 4
Rounded to 2 significant figures, 0.004560 is 0.0046, or 4.6 × 10⁻³ in scientific notation.
Use it for chemistry and physics answers, where a result should keep the same number of significant figures as the least precise measurement.
Questions people ask
How many significant figures does 0.004560 have?
Four: 4, 5, 6 and the final 0. The leading zeros only hold the place; the trailing zero after the decimal point counts.
Are trailing zeros significant?
After a decimal point, yes: 5.200 has four. In a whole number without a point, such as 5200, they are ambiguous, so it has 2 to 4. Writing 5200. or 5.20 × 10³ makes it clear.
Are zeros between digits significant?
Always. 405 has three significant figures and 1.007 has four.
How do I round to significant figures?
Keep that many digits from the first non-zero one and round the next digit. 0.004560 to 2 sig figs is 0.0046, and 123,456 to 3 is 123,000.
About this calculator
Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem