Report a measured value
Round a laboratory or engineering value to the precision required by an assignment, report, or measurement method.
Sig Fig Calculator
Enter a decimal or scientific-notation value and choose the precision to get a rounded result with significant figures preserved.
Round a Number to Significant Figures
Enter a decimal or scientific-notation value and choose how many significant figures to keep.
The rounded decimal, scientific notation, and detected input precision will appear here.
How to Use Sig Fig Calculator
1
Enter the Number
Use an ordinary decimal or notation such as 1.2345e6.
2
Choose Significant Figures
Select a whole-number precision from 1 through 15.
3
Review Both Formats
Compare the rounded decimal with scientific notation, which makes retained trailing zeros explicit.
Sig Fig Calculator Features
- Exact decimal-string rounding
- 1–15 significant figures
- NIST half-even tie handling
- Decimal and scientific-notation output
Common Use Cases
Check a halfway rounding case
See how an exact trailing 5 behaves under half-even rounding instead of assuming every 5 rounds upward.
Limits and Important Notes
Result type: Exact calculation
Calculation Details
- Locate the first nonzero digit; leading zeros are placeholders, not significant figures.
- Keep the requested number of significant digits.
- Inspect the discarded digits and apply half-even rounding, then rebuild decimal and scientific notation.
Formula
Keep the requested leading significant digits; if the discarded portion is exactly halfway, make the final retained digit even.
Rounding
Exact halfway cases follow NIST half-even rounding. The calculator supports 1–15 significant figures.
Default Assumptions
- The digits entered by the user reflect the intended source value and precision.
- Scientific notation uses base 10.
- The tool rounds one number; it does not propagate measurement uncertainty through a longer calculation.
Verified Example
Inputs: Value 0.004565 and 3 significant figures.
Calculation: Leading zeros are ignored; keep 456 and inspect the exact trailing 5. Because the retained 6 is even, it stays unchanged.
Result: 0.00456, or 4.56 × 10^-3.
Sources and Version
Version: NIST half-even rounding
Last verified: 2026-08-15
Update responsibility: OnlineTool.me
- NIST Guide to the SI, Chapter 7 — National Institute of Standards and Technology (accessed 2026-08-15)
- NIST SP 811 Appendix B — National Institute of Standards and Technology (accessed 2026-08-15)
- The calculator does not decide how many significant figures a scientific result should use.
- A whole number such as 1200 can be visually ambiguous in plain notation; use the scientific-notation result to show intended trailing-zero significance.
- This is a rounding aid, not an uncertainty or error-propagation calculator.
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