The rules for determining the number of Significant Figures after a calculation is performed with measurements:

  Addition and Subtraction

  • When two or more numbers are added or subtracted the final answer is rounded off to the same decimal place as the number having its last significant digit the furthest to the left.


If you have the numbers 4.501 and 90.2 added together you will get 94.7 because the last column that both numbers use is the tenths place.

  Multiplication and Division

  • Significant digits in Multiplication and Division are determined by the number of significant digits in each of the numbers in the calculation. The answer must have the same amount of significant digits as the number in the calculation with the least amount of significant digits.


If you multiply the numbers 500 and 256 together the answer would be 100000 because 500 only has one significant digit so the answer can have only one significant digit.

If you divide 1575 (four significant figures) by 17.6 (three significant figures), you round your answer to 89.5 (from 89.48863) so that it will have 3 significant digits.