RULES FOR DETERMINING SIGNIFICANT FIGURES
1. All non-zero numbers are significant: EX: 12.34 has 4 significant figures.
2. All internal zeros are significant: EX: 10.23 has 4 significant figures
3. All preceding zeros are insignificant: EX: 0.0001234 has 4 significant figures
4. Trailing zeros are significant only if
a. They are preceded by an internal decimal point: EX: 12.3400 has 6 significant figures
but 123400 has only 4 significant digits.
b. They are followed by a unit: EX: 12.00 miles has 4 significant figures.
5. Exact numbers have infinite significance. Exact numbers are numbers generated by
definitions. For example the equivalence equation, 1 ft = 12 inches, both the 1 and the 12
have infinite significance. This means they never determine the significance of an
operation.
6. In multiplication and division the answer can have only as many significant figures as the
least significant operator: 12.345 x 6.75 = 83.32875; to the correct significance = 83.33.
7. In addition and subtraction the answer can have no more or less decimal places than the
operator with the least number of decimal places: EX: 12.345 – 6.75 = 5.595; to the proper
significance = 5.60.