Significant Figures Calculator

Significant figures (sig figs) are the meaningful digits in a measurement that convey precision. Rules: all non-zero digits are significant, zeros between non-zero digits are significant, leading zeros are not significant, trailing zeros after a decimal point are significant. Example: 0.00450 has 3 sig figs (4, 5, and the trailing 0).

Count all digits starting from the first non-zero digit. 120.0 has 4 sig figs. 0.0035 has 2 sig figs. 1000 is ambiguous (1-4 sig figs depending on context — use scientific notation to clarify: 1.000 x 10^3 = 4 sig figs). The calculator counts sig figs for any number and explains which digits are significant and why.

The result has the same number of sig figs as the input with the fewest sig figs. 2.5 (2 sig figs) x 3.42 (3 sig figs) = 8.55, rounded to 8.6 (2 sig figs). This rule ensures the result does not imply more precision than the least precise measurement used in the calculation.

The result is rounded to the same decimal place as the input with the fewest decimal places. 12.11 + 0.3 = 12.41, rounded to 12.4 (one decimal place, matching 0.3). Note: addition/subtraction uses decimal places, not sig fig count. These are different rules — the calculator applies both correctly.

Sig figs communicate measurement precision. Reporting a length as 5.00 cm (3 sig figs) means the measurement is precise to the nearest 0.01 cm. Reporting 5 cm (1 sig fig) implies precision only to the nearest cm. Using proper sig figs prevents overstating the accuracy of calculated results.