Significant Figures Calculator
Significant figures (or significant digits) represent the precision and reliability of a measured or calculated value. This calculator takes any number and rounds it to a specified number of significant figures, then displays the result in both standard and scientific notation. Significant figures indicate how many digits carry meaningful information: all non-zero digits are always significant, zeros between non-zero digits are significant, leading zeros are not significant, and trailing zeros after a decimal point are significant. For example, 0.00450 has 3 significant figures (4, 5, and the trailing 0), while 4,500 might have 2, 3, or 4 depending on context. Rounding to appropriate significant figures prevents false precision and is essential in science and engineering.
Significant figures rules
All non-zero digits (1-9) are significant
Zeros between non-zero digits are significant
Leading zeros are NOT significant
Trailing zeros after decimal point ARE significant
Trailing zeros in whole numbers are ambiguous
Significant figures examples
| Number | Significant Figures | Count |
|---|---|---|
| 0.0045 | 4, 5 | 2 |
| 0.00450 | 4, 5, 0 | 3 |
| 4500 | 4, 5 (and maybe zeros) | 2-4 |
| 45.00 | 4, 5, 0, 0 | 4 |
| 1200.00 | 1, 2, 0, 0, 0, 0 | 6 |
| 0.00120 | 1, 2, 0 | 3 |
Significant figures calculator: frequently asked questions
What are significant figures?
Significant figures are the digits in a number that carry meaningful information. They indicate the precision of a measurement or calculation. For example, 0.0045 has 2 significant figures (4 and 5), while 4500 might have 2, 3, or 4 significant figures depending on context.
How do you count significant figures?
Rules: All non-zero digits are significant. Zeros between non-zero digits are significant. Leading zeros are not significant. Trailing zeros after a decimal point are significant. Trailing zeros in a whole number may or may not be significant (context dependent).
Why are significant figures important?
Significant figures indicate the precision and reliability of a measurement. They prevent false precision by rounding results appropriately. In science, reporting too many significant figures suggests unwarranted precision.
What is the difference between precision and accuracy?
Precision refers to the number of significant figures and how close repeated measurements are to each other. Accuracy refers to how close a measurement is to the true value. Significant figures reflect precision, not accuracy.
How do you round to significant figures?
Count the required number of significant figures from the first non-zero digit. Look at the next digit: if it is 5 or higher, round the last kept digit up. If it is 4 or lower, keep the last digit as is.
Official sources
- Significant figures: NIST Special Publication 330.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.