Significant Figures Calculator

Significant figures (sig figs) are the meaningful digits in a number that contribute to its precision. In 0.00450: the significant figures are 4, 5, and 0 (trailing zero after decimal counts), giving 3 sig figs. Leading zeros are never significant.

All non-zero digits are significant. Zeros between non-zero digits are significant (305 = 3 sig figs). Leading zeros are not significant (0.005 = 1 sig fig). Trailing zeros after a decimal point are significant (2.50 = 3 sig figs).

Count from the first non-zero digit. Round the last significant digit based on the next digit. 0.004562 to 2 sig figs: count 4 and 5, next digit is 6 (≥5), round up → 0.0046.

For multiplication/division: result has the same number of sig figs as the input with the fewest. For addition/subtraction: result has the same number of decimal places as the input with the fewest. 2.5 × 3.42 = 8.6 (2 sig figs).

Sig figs communicate measurement precision. Reporting a length as 5.00 cm (3 sig figs) means it was measured to the nearest 0.01 cm. Reporting 5 cm (1 sig fig) means only to the nearest cm. Over-reporting precision is misleading.