Significant Figures Calculator

Significant figures (sig figs) are the meaningful digits in a number that reflect measurement precision. Non-zero digits are always significant. Zeros between non-zero digits are significant. Trailing zeros after a decimal point are significant. Leading zeros are never significant.

0.00470 has 3 significant figures: 4, 7, and the trailing 0 after the 7. The leading zeros (0.00) are not significant — they are just placeholders showing the decimal place. The trailing zero IS significant because it shows precision to the ten-thousandths place.

Multiplication/Division: round to the fewest sig figs in the inputs. 2.5 × 3.42 = 8.6 (2 sig figs). Addition/Subtraction: round to the fewest decimal places in the inputs. 12.52 + 1.1 = 13.6 (1 decimal place). Scientific notation makes sig figs unambiguous: 3.50 × 10^4 has exactly 3 sig figs.

Find the 3rd significant digit, then look at the next digit. If it is 5 or more, round up; if less than 5, round down. Examples: 0.004726 → 0.00473. 12,456 → 12,500. 1.2349 → 1.23. Zeros used as placeholders do not count, only measurement-meaningful digits do.

They communicate the precision of a measurement. Writing 12.5 g implies precision to ±0.05 g; writing 12.500 g implies ±0.0005 g. In engineering and science, false precision can lead to errors. A calculated result cannot be more precise than the least precise measurement it came from.