Significant figures communicate how precise a measurement is. Writing 2.50 m instead of 2.5 m says you measured to the nearest centimetre. Results of calculations should not claim more precision than the data.
How to use the Significant Figures Calculator: Sig Fig
- Number or expression
- Round to significant figures (0 = just count)
Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.
How it works
The number is read exactly as typed, so trailing zeros and a decimal point are respected. For an expression, multiplication and division keep the fewest significant figures and addition and subtraction keep the fewest decimal places.
Formula
Counting: non-zero digits count; zeros between them count; leading zeros never count; trailing zeros count after a decimal point
× ÷: fewest significant figures · + −: fewest decimal places
Worked example
Inputs: Number or expression: 0.004520; Round to significant figures (0 = just count): 0.
Results: Result = 4; Significant figures = 4 significant figures; Scientific notation = 4.52 × 10⁻³; E-notation = 4.52e-3; Explanation = Counting rules: non-zero digits count; zeros between them count; leading zeros never count; trailing zeros count only after a decimal point..
Key terms
- Significant figures
- The digits that carry meaningful precision.
Frequently asked questions
How many sig figs does 0.004520 have?
Four: 4, 5, 2 and the trailing 0.
Is 1200 two or four significant figures?
Ambiguous: write 1.2 × 10³ (two) or 1.200 × 10³ (four).
How many sig figs in 3.14 × 7.58?
Three, the fewest of the inputs.
Do exact numbers limit sig figs?
No. Counted or defined quantities (12 eggs, 100 cm per m) have unlimited precision.
Sources
Guides on this topic
- Percent Error vs Percent Difference: Formulas, Examples and When to Use Each: Percent error divides by a true value; percent difference divides by the average of two measurements. Here is when to use each, with lab examples.