
All digits (1,2,3,4,5,6,7,8,9) are significant. However, zeros may or may not be significant. In case of zeros, the following rules may be adopted.

A zero between two significant figures is itself significant.

Zeros to the left of significant figures are not significant. For example, none of the zeros in 0.00467 or 02.59 is significant.

Zeros to the right of a significant figure may or may not be significant. In decimal fraction, zeros to the right of a significant figure are significant. For example, all the zeros in 3.570 or 7.4000 are significant.

When a measurement is recorded in scientific notation or standard form, the figures other than the powers of ten are significant figures. For example, a measurement recorded as 8.70 × 10^{2} kg has three significant figures.

When adding or subtracting, round the answer to the least number of decimal places. Example 1: 1.457 + 83.2 = 84.657, the answer will be reounded as 84.7 (three significant figures) because 83.2 (three significant figures) has least number of decimal places so the answer will be rounded as three significant figures. Example 2: 0.0367  0.004322 = 0.032378, here the answer will be 0.0324 (three significant figures), because 0.0367 has the least decimal places and three significant figures.

When multiplying or dividing, round the answer to the least number of significant digits.
Example 1: 4.36 X 0.000 13 = 0.000 5668 , answer will be 0.000 57
4.36 has three significant figures, 0.00013 has two significant figures, so the answer will be 0.000 57 (two significant figures)
Example 2: 12.300 / 0.0230 = 534.78261, answer will be 535
In calculation, 0.0230 has three significant figures, which is the least significant figures in the calculation, so the answer will be 535 with three significant figures.
