Precision & Significant Figures
Understanding measurement precision, significant figures, and proper rounding in scientific work.
Why & What
Precision refers to the degree of exactness of a measurement. No measurement is perfectly accurate—every instrument has limitations. Significant figures communicate the precision of a measurement.
Accuracy is how close a measurement is to the true value, while precision is how close repeated measurements are to each other. Understanding the difference is crucial in science and engineering.
Significant Figures Rules
1234 has 4 significant figures
1002 has 4 significant figures
0.0025 has 2 significant figures
2.500 has 4 significant figures
1500 could be 2, 3, or 4 sig figs. Use scientific notation: 1.50 × 10³ (3 sig figs)
Significant Figures Counter
Round to Significant Figures
Examples
| Number | Sig Figs | Explanation |
|---|---|---|
| 123 | 3 | All non-zero digits count |
| 1230 | 3* | Trailing zero ambiguous |
| 1230.0 | 5 | Decimal makes trailing zeros significant |
| 0.00456 | 3 | Leading zeros don't count |
| 0.004560 | 4 | Trailing zero after decimal counts |
| 1.00 × 10⁴ | 3 | Scientific notation is unambiguous |
Calculation Rules
Result should have the same number of sig figs as the least precise input.
2.5 × 3.42 = 8.55 → 8.6 (2 sig figs, limited by 2.5)
Result should have the same decimal places as the least precise input.
12.52 + 1.3 = 13.82 → 13.8 (1 decimal place, limited by 1.3)
Limitations & Disclaimer
- This tool uses simplified rules; edge cases may exist.
- Trailing zeros in integers are assumed non-significant without a decimal.
- For critical applications, consult established scientific standards.
- For educational purposes only.