Significant Figures Calculator
Add, subtract, multiply, or divide any two numbers and receive the correctly rounded result based on significant figures rules. Accepts standard numbers, scientific notation, and e notation.
Significant Figures Rules Reference
The significant figures rules reference table below shows common examples so you can quickly verify how many sig figs a number contains.
| Number | Sig Figs | Significant Digits |
|---|---|---|
| 81 | 2 | 8, 1 |
| 26.2 | 3 | 2, 6, 2 |
| 0.007 | 1 | 7 |
| 5200.38 | 6 | 5, 2, 0, 0, 3, 8 |
| 380.0 | 4 | 3, 8, 0, 0 |
| 78800 | 3 | 7, 8, 8 |
| 78800. | 5 | 7, 8, 8, 0, 0 |
| 3.5 x 103 | 2 | 3, 5 |
What Are Significant Figures?
Significant figures are the digits in a number that carry meaningful information about the precision of a measurement or calculation. They tell you how well a value is known, not just what value it represents.
In scientific and engineering contexts, reporting too many or too few significant figures communicates either false precision or an unnecessary loss of information. The rules ensure that calculated results reflect only the precision available from the input measurements.
The Four Significant Figures Rules
- Non-zero digits are always significant.
- Zeros between non-zero digits are always significant (e.g. 3003 has 4 sig figs).
- Leading zeros are never significant (e.g. 0.0056 has 2 sig figs).
- Trailing zeros are significant only when a decimal point is present (e.g. 380.0 has 4 sig figs but 380 has 2 or 3 depending on context).
Rules for Addition and Subtraction
When adding or subtracting, identify the number with the fewest decimal places. Round the final answer to that same decimal position, not to a number of significant figures.
Example: 7 oz + 2 oz + 0.063 oz = 9.063 oz, rounded to the ones place because 7 oz has no decimal places, giving 9 oz.
Rules for Multiplication and Division
When multiplying or dividing, count the significant figures in each number. Round the final answer to whichever input has the fewest significant figures.
Example: 52 Hz has 2 sig figs. 343 m/s has 3 sig figs. Their product or quotient is rounded to 2 sig figs.