All nonzero digits are significant
Zeros between nonzero 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 significant unless specified
In multiplication and division, round to the least number of significant figures
In addition and subtraction, round to the least number of decimal places
For exact numbers, keep all digits
Use scientific notation to show the intended significant figures
Round only at the final step whenever possible