Uncertainty & measurement
Significant figures
Round a written number to significant figures.
Your measurements
Number formats & units
Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.
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Result & working
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Interpretation & assumptions
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Formula & example
The relationship
Keep N significant digits; round up if the first discarded digit is 5–9.
What the variables mean
| Symbol | Meaning |
|---|---|
| Requested number of significant figures, from 1 to 15. | |
| e notation | 1.20e-3 means 1.20 × 10⁻³. The exponent does not change the significant-figure count. |
Worked example
- Number to round
- 0.004520
- Significant figures (1–15)
- 3
4.52 × 10^-3
Follow the example steps
- Input: 0.004520
- Requested significant figures: 3
- Rounded scientific notation: 4.52 × 10^-3
- The written input indicates 4 significant figures. Leading zeros are not significant; zeros between significant digits are significant. Trailing zeros in a decimal or scientific-notation mantissa express precision. The first discarded digit determines rounding. Exact halfway cases round away from zero. Adding zeros cannot improve measurement precision.
Common mistakes
Leading zeros are placeholders; decimal trailing zeros can matter.
Incorrect approach
0.00450 has 5 significant figures.
Correct approach
0.00450 has 3 significant figures: 4, 5, 0.
More checks before you submit
- Significant figures and decimal places are different.
- Adding trailing zeros does not create more accurate measurements.
- Keep unrounded values during intermediate calculations.
- A measured zero needs resolution or an absolute uncertainty to communicate precision.
Method notes
Use significant figures to report a result to an appropriate precision. Leading zeros locate the decimal point: 0.004520 has four significant figures. The zero between 1 and 2 in 1.02 is significant.
Trailing zeros in 1200 are ambiguous without more context. Write 1.2 × 10³ for two significant figures or 1.200 × 10³ for four. This calculator rounds decimal strings directly, so an exact decimal tie such as 1.005 to three significant figures becomes 1.01.