Experimental data & uncertainty · SL/HL
Significant figures
Round a written number to significant figures.
Your values
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 the requested number of significant digits; use the first discarded digit to round.
What the variables mean
| Symbol | Meaning |
|---|---|
| significant digit | A digit conveying the precision represented by the written number. |
Worked example
- Number
- 0.004560
- Significant figures
- 3
4.56 × 10^-3
Follow the example steps
- Input: 0.004560
- Requested significant figures: 3
- Rounded: 4.56 × 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
- Leading zeros are placeholders.
- Trailing zeros in a decimal can communicate precision.
Method notes
Course calculations should preserve guard digits internally and round final reported quantities appropriately.