Identify all non-zero digits as significant
Count zeros between non-zero digits as significant
Count leading zeros as not significant
Count trailing zeros as significant only if a decimal point is present
In numbers without a decimal point, trailing zeros may be ambiguous
Count exact numbers and defined constants as having infinite significant figures
For multiplication and division, keep the same number of significant figures as the factor with the fewest significant figures
For addition and subtraction, keep the same number of decimal places as the term with the fewest decimal places
Round the final result only after completing the calculation
Use scientific notation to make significant figures clear when needed
Check the final digit to decide whether to round up or down
When in doubt, follow the rules for the type of operation being performed