Tools HubSignificant Figures Calculator
Count significant figures, round to a chosen precision, and apply the multiplication/division or addition/subtraction rules. Switch between half-up and JIS Z 8401 half-even rounding; scientific notation is shown alongside.
Try an example
Result
Worked steps
Approximate results are displayed to at most 10 significant digits. Measurement significant figures and uncertainty are not inferred.
Formula and example
Count significant figures from the first nonzero digit to the last. For multiplication and division, round the result to the fewest significant figures; for addition and subtraction, to the fewest decimal places. Ambiguous integers can be checked in scientific notation.
桁数 = 最初の0でない数字から末尾まで数える／乗除 = 有効桁数の最小、加減 = 小数位の最小
1.23 × 4.5 → 2 sig figs → 5.5 (12.34 + 1.2 → 1 decimal place → 13.5)
- Count digits0.00120 → 3 significant figures (1.20 × 10⁻³)
- Round to 3 digits3.14159 → 3.14
- Mul/div rule1.23 × 4.5 = 5.535 → 2 sig figs → 5.5
- Add/sub rule12.34 + 1.2 = 13.54 → 1 decimal place → 13.5
Common mistakes
- In an integer without a decimal point, trailing zeros are not significant: 1200 has two, while 1200. has four.
- Multiplication/division uses significant digits, addition/subtraction uses decimal places. Mixing them up produces wrong results.
- Round only once, at the end. Rounding intermediate values accumulates error.
Check the assumptions
Applies to measured (approximate) values. Trailing zeros in integers without a decimal point are not counted, and scientific notation is shown to remove ambiguity. One binary operation is applied and rounded once at the end. Floating-point precision limits values to 15 significant digits.
Calculations run in your browser. Inputs and results are not sent or saved.
OpenStax · College Physics 2e — Accuracy, Precision, and Significant Figures ↗How to use
- 1
Enter values and units
Use the example or enter your own conditions.
- 2
Calculate
Check the result and each calculation step.
- 3
Check assumptions
Review applicability and display precision, then copy inputs and results if needed.
Features
- Worked steps and unit conversions
- No account; calculation stays in your browser
- Copy inputs and results together
Use cases
Check your working
Compare formula substitutions and units with your own calculations.
Details
Applies to measured (approximate) values. Trailing zeros in integers without a decimal point are not counted, and scientific notation is shown to remove ambiguity. One binary operation is applied and rounded once at the end. Floating-point precision limits values to 15 significant digits.
FAQ
How many significant figures does 1200 have?
Without a decimal point, the trailing zeros are placeholders, so it counts as two. Write 1.200×10³ to show four significant figures.
What is the difference between half-up and half-even rounding?
For an exact 5, half-up always rounds up, while JIS Z 8401 half-even rounds toward an even last digit (2.5→2, 3.5→4). Half-even avoids statistical bias in repeated rounding.
Are results exact?
Results use floating-point approximations, displayed to at most 10 significant digits. Measurement significant figures and uncertainty are not inferred.
Are inputs saved?
Inputs and results are not sent to a server or saved. They disappear when you leave the page.
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Verified: Digit counting (0.00120 to 3, 1200 to 2), half-up and half-even rounding, the fewest-significant-figures and fewest-decimal-places rules, division by zero and digit-range errors are covered by automated tests