Significant Figures in a Calculation Calculator
Multiply or divide two measurements and round the answer to the correct number of significant figures — the fewest that either input carries.
How it works
For × and ÷: keep the fewest significant figures of the inputs · result rounded to min(sf₁, sf₂)
When you multiply or divide, the answer can be no more precise than your least precise measurement, so it is rounded to the smallest significant-figure count among the inputs. This differs from addition and subtraction, which track decimal places instead. Keeping too many digits fakes a precision the data never had — a common mistake when copying a long calculator readout.
Worked example
Multiply 4.56 (3 sig figs) by 1.4 (2 sig figs). The raw product is 6.384, but the least precise input has only 2 significant figures, so the answer is rounded to 6.4.
Sources: Significant figures — Wikipedia
Frequently asked questions
Why does multiplication use significant figures, not decimal places?
Multiplying and dividing scale relative uncertainty, which significant figures measure. Adding and subtracting instead depend on the position of the last certain digit, so those follow a decimal-place rule.
Why do I enter the sig-fig count myself?
A plain number like 1.4 loses information about trailing zeros — 1.40 and 1.4 look different on paper but the same to a calculator. Telling it the count keeps the rounding honest to your actual measurement.
Do exact numbers count?
No. Counted quantities and defined constants (like 12 in a dozen, or 100 cm in a metre) are treated as having unlimited significant figures, so they never limit the result — only measured values do.
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