Significant Figures Calculator
Count sig figs with digit-by-digit highlighting, round to any precision, or do arithmetic with proper sig fig rules.
How It Works
Significant figures indicate the precision of a measurement. The rules are straightforward: all non-zero digits are significant, zeros between non-zero digits (captive zeros) are significant, and trailing zeros after a decimal point are significant. Leading zeros are never significant.
When performing arithmetic, the result must reflect the precision of the least precise input. For addition and subtraction, round to the fewest decimal places. For multiplication and division, round to the fewest significant figures.
The ambiguous case is trailing zeros without a decimal point (like 100). By convention this has 1 sig fig, but writing 100. (with a trailing decimal) makes it 3 sig figs. Scientific notation (1.00 × 10²) is the clearest way to show precision.