Significant Figures Calculator
Count the significant figures in any number, round to 1-15 sig figs, and apply the sig-fig rules to arithmetic.
Type a number above to count its significant figures.
Significant figures —
significant not significant
- Decimal places
- —
- Order of magnitude
- —
- Rounded to 3 s.f.
- —
- Scientific notation
- —
- E-notation
- —
- Exact value
- —
Why
Type a number to see how many significant figures it has.
Significant figure arithmetic
- Answer (sig figs applied)
- —
- Unrounded
- —
- Significant figures
- —
Enter two values to apply the sig-fig rules.
How it works
Type any number — plain, decimal or scientific like 6.022e23 — and the counter
applies the standard rules instantly: every non-zero digit is significant, zeros between
significant digits are significant, leading zeros never are, and trailing zeros count only
when the number contains a decimal point. That is why 0.004560 has four
significant figures while 1200 has only two — unless the trailing zeros were
measured, which is what the checkbox is for. The digit-by-digit breakdown highlights exactly
which digits are being counted, so you can check your own working.
The rounder gives you the number to 1–15 significant figures in plain decimal, proper scientific notation and e-notation, and the arithmetic panel applies the two lab rules for you: addition and subtraction keep the fewest decimal places, multiplication and division keep the fewest significant figures. Everything is calculated in JavaScript inside your own browser — nothing is uploaded, there is no sign-up and there are no ads.
Frequently asked questions
How many significant figures does 0.004560 have?
Four. The three leading zeros only place the decimal point and never count, while the trailing zero does count because the number is written with a decimal point — so the significant digits are 4, 5, 6 and 0. The digit-by-digit breakdown on this page strikes through the zeros that do not count so you can check it at a glance.
Are the trailing zeros in 1200 significant?
By the usual convention, no: a whole number with no decimal point has ambiguous trailing zeros, so 1200 is treated as 2 significant figures. If those zeros were actually measured, tick "trailing zeros in whole numbers are significant" to count all 4, or write the number as 1.200 × 10³ in scientific notation, which is never ambiguous.
What are the significant figure rules for adding and multiplying?
Addition and subtraction keep the fewest decimal places of the inputs — 12.11 + 0.3 = 12.4, not 12.41. Multiplication and division keep the fewest significant figures — 4.56 × 1.4 = 6.4, not 6.384. The arithmetic panel applies whichever rule fits your operation and spells out the reasoning underneath the answer.