All non-zero digits are significant
Zeros between non-zero digits are significant
Leading zeros are not significant
Trailing zeros are significant only if a decimal point is present
Trailing zeros in a whole number without a decimal point are not always significant
Exact counts and defined constants have infinite significant figures
In scientific notation, all digits in the coefficient are significant
For multiplication and division, the result has the same number of significant figures as the least precise value
For addition and subtraction, the result has the same number of decimal places as the least precise value
When in doubt, use scientific notation to show the intended significant figures