Rounding and Significant Figures Checker
Rounds numbers exactly as written to decimal places or significant figures, with a stated tie rule and no binary rounding surprises.
Read as text, so trailing zeros and exponents are kept exactly.
Result
Enter a number to round it.
Rounding changes how a value is written, not how accurately it was measured. Ties are decided on the digits you typed, never on a binary approximation.
How the method works
A fixed worked example to explain the method — it is not your result.
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Type the number exactly as written — trailing zeros and exponents count (0.004560, 6.02e23).
- Choose decimal places or significant figures and how many.
- Choose the tie rule for values ending exactly in 5: half away from zero (the default) or half to even.
- Read the rounded value, the exact change, and the other mode for comparison. Paste a list for batch rounding.
How it works
The number is read as a decimal string and rounded with exact integer arithmetic, so a tie is decided on the digits you typed. Ordinary binary arithmetic gets 1.005 to 2 decimal places wrong (it gives 1.00, because 1.005 is stored as 1.00499…).
Significant figures start at the first non-zero digit; trailing zeros after a decimal point are significant, while in a bare integer such as 1200 they are ambiguous.
Requested zeros are kept (2 → 2.000). When a significant-figure result would need zeros before the decimal point — 999.5 to 3 figures — fixed notation cannot show them, so scientific notation is used: 1.00e3.
Rounding changes how a value is written, not how accurately it was measured.
Worked example
1.005 and 999.5. 1.005 to 2 decimal places is 1.01 (half away from zero) or 1.00 (half to even); −1.005 gives −1.01 or −1.00. 123.456 to 4 significant figures is 123.5, 0.004560 to 3 is 0.00456, and 999.5 to 3 is 1.00e3.
Common mistakes
- Rounding intermediate results instead of only the final answer.
- Dropping meaningful trailing zeros: 12.50 m is not the same statement as 12.5 m.
- Assuming every program breaks ties the same way — spreadsheets, calculators and code differ.
Frequently asked questions
Significant figures or decimal places?
Use significant figures to express the reliability of a measurement (e.g. a distance good to 4 sig figs); use decimal places when a specification fixes the precision (e.g. levels to 3 dp / the nearest millimetre).
Should I round during the calculation?
No. Carry full precision through every step and round only the final answer — rounding intermediate values introduces error that can push the result outside tolerance.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
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Cite this tool
Zerdly. (2026). Rounding and Significant Figures Checker. Retrieved from https://www.zerdly.com/tools/rounding-and-significant-figures-checker/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.