Sig Fig Calculator
Count the significant figures in a number and round it to any number of significant figures. Example: 0.004560 has 4 significant figures, and rounded to 2 it becomes 0.0046.
Type the problems from this lesson and check each step.
Show steps
How to use the Sig Fig Calculator
- Type the number, including any decimal point or e-notation.
- Choose how many significant figures to round to.
- Press Calculate for the count and the rounded value.
Formula and method
Significant figures: all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point. Leading zeros do not count. To round, keep the first n significant digits and round the last one.
Worked examples
| Number | Sig figs | Why |
|---|---|---|
| 0.004560 | 4 | Leading zeros skipped; trailing 0 counts |
| 1200 | 2 | Trailing zeros are placeholders |
| 1200. | 4 | Decimal point makes them count |
| 100.0 | 4 | Trailing zero after the point counts |
| 3.00e5 | 3 | Digits in the mantissa count |
| 40.05 | 4 | Zero between digits counts |
The five rules
Non-zero digits count. Zeros between non-zero digits count. Leading zeros do not. Trailing zeros count only with a decimal point. Exact numbers, such as counts, have unlimited significant figures.
Sig figs in calculations
When multiplying or dividing, the answer has as many significant figures as the input with the fewest. When adding or subtracting, match the least number of decimal places.
Frequently asked questions
What are significant figures?
The digits in a number that carry meaningful precision.
How many sig figs are in 0.00250?
Three.
Do trailing zeros count?
Only if there is a decimal point.
How do I round to 3 sig figs?
Keep three significant digits and round the last one by the next digit.
Do leading zeros count?
No.
Do exact numbers have sig figs?
They are treated as unlimited.
Sources
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