Significant Figures Calculator
Count significant figures in any number and round to a specified number of significant figures. This calculator handles integers, decimals, and scientific notation.
How to Use This Calculator
- Enter any number in the input field (supports decimals and scientific notation)
- Click "Count Significant Figures" to see how many sig figs the number contains
- To round, specify the desired number of significant figures
- Optionally enable scientific notation for the result
- Click "Round Number" to see the rounded result
What Are Significant Figures?
Significant figures (or significant digits) are the digits in a number that carry meaningful information about its precision. They include all certain digits plus one uncertain digit.
Rules for Counting Significant Figures
- Non-zero digits are always significant (e.g., 123 has 3 sig figs)
- Zeros between non-zero digits are significant (e.g., 1002 has 4 sig figs)
- Leading zeros are not significant (e.g., 0.0025 has 2 sig figs)
- Trailing zeros in a decimal are significant (e.g., 1.200 has 4 sig figs)
- Trailing zeros in a whole number may or may not be significant (e.g., 1200 is ambiguous)
Examples
- 123.45 → 5 significant figures
- 0.00456 → 3 significant figures
- 100.0 → 4 significant figures
- 1.23e5 → 3 significant figures
- 5000 → 1 significant figure (ambiguous, could be 1-4)