Rules governing significant figures
Basic rules
1.
Any non-zero digit is significant.
2.
Zeros between non-zero digits are always significant.
Example: 3,606 has 4 significant figures.
3.
Zeros that indicate the decimal point are not
significant.
Example: 360,600 has 4 significant figures.
4.
Zeros following a decimal are significant.
Example: 3.60 has 3 significant figures but 3.6 has 2.
5.
Zeros appearing before a non-zero digit are not
significant.
Example: 0.009 only has 1 significant figure.
Addition and subtraction rule
The number of significant figures in a sum or difference is
equal to that of the least accurate measurement in the
equation. The answer must contain the same number of
decimal places as the least accurate measurement.
Example: Without using significant figures: 606.02 – 65.3 =
540.72
Using significant figures: 540.7
Multiplication and division rule
The number of significant figures in a product or quotient is
equal to that of the least accurate measurement in the
equation. The answer must contain the same number of
significant figures as the least accurate measurement.
Example: Without using significant figures: 606.02 × 63 =
38,179.26
Using significant figures: 38,000 (has only 2 significant figures)