Significant Figure Rules!
Every non-zero is significant.
Zeros between non-zeros are significant.
Zero in front of non-zeros are NOT significant.
Zeros at the end of a number AND to the right of a decimal are always significant.
Zeros at the end of a measurement AND to the left of a decimal are not significant if they are used to show magnitude.
Measurements have unlimited significant figures in these two cases:
exactly defined quantities within a system of measurement
An answer for a calculation cannot be more precise (have more significant figures) than the least precise measurement from which it was calculated. (“Least precise” means least number of significant figures.)
With calculations, first, ask yourself if you are doing addition/.subtraction or multiplication/division.
ADDITION/SUBTRACTION: Count decimal places, not significant figures. You answer should have the same number of decimal places as the fewest in your original problem.
MULTIPLICATION/DIVISION: Count significant figures. You answer should have the same number of sig figs as the least of your original problem.