Significant Figures Calculator

Significant figures (sig figs) are the meaningful digits in a number that carry precision about a measurement. They include all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point. Leading zeros (like the 0s in 0.0045) are never significant. See also our use the Round to Nearest Tenth Calculator.

The key rules are: (1) All non-zero digits are significant. (2) Zeros between non-zero digits are significant (e.g., 3003 has 4 sig figs). (3) Leading zeros are never significant (e.g., 0.009 has 1 sig fig). (4) Trailing zeros are only significant when a decimal point is present (e.g., 6750. has 4 sig figs, but 6750 has 3).

The number 100 has 1 significant figure. The trailing zeros are not significant because there is no decimal point. To indicate that all three digits are significant, you would write 100. (with a decimal point) or use scientific notation: 1.00 × 10².

100.00 has 5 significant figures. The decimal point makes all trailing zeros significant, so every digit — 1, 0, 0, 0, 0 — counts.

0.01 has 1 significant figure. The leading zeros (0.0) simply indicate the position of the decimal and carry no precision information. Only the digit 1 is significant.

0.00208 has 3 significant figures: 2, 0, and 8. The four leading zeros (0.00) are not significant — they just place the decimal. The zero between 2 and 8 is significant because it falls between two non-zero digits.

2648 rounded to 3 significant figures is 2650. You keep the first three significant digits (2, 6, 4) and look at the next digit (8) to decide rounding — since 8 ≥ 5, you round up the 4 to 5, giving 2650.

Scientific notation is actually the clearest way to express significant figures. In a number like 3.50 × 10³, every digit shown in the coefficient (3, 5, 0) is significant — giving exactly 3 sig figs. This eliminates ambiguity about whether trailing zeros count.