Rule #1

ALL non-zero digits DO count!

​498

​

​

​3 sig figs!

​2 sig figs!

​1 sig fig!

​79

​2

Rule #2

Zeros to the right of decimal and a significant digit DO count.

​498.00

​

​

​4 sig figs!

​5 sig figs!

​3 sig figs!

​ 79.0

​2.000

Rule #3

Zeroes between significant figures DO count

​409

​

​

​5 sig figs!

​3 sig figs!

​4 sig figs!

​7006

​20004

Rule #3

Zeroes between significant figures DO count

​409

​

​

​5 sig figs!

​3 sig figs!

​4 sig figs!

​7006

​20004

Rule #4

Zeroes at the end of a whole number DO NOT count.

​400

​

​

​1 sig fig!

​1 sig fig!

​2 sig figs!

​7500

​20

Rule #5

Zeroes in front of a number as placeholders DO NOT count.

0.004

​

​

​2 sig figs!

​1 sig fig!

​4 sig figs!

​0.07500

​0.20

Significant figures in addition and subtraction

For addition and subtraction use the following rules: Count the number of significant figures in the decimal portion ONLY of each number in the problemAdd or subtract in the normal fashionYour final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem.

Significant Figures in Multiplication and Division

For multiplication and division use the following rule: 

The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. (You are now looking at the entire number, not just the decimal portion)

*This means you have to be able to recognize significant figures in order to use this rule*      

Example: 5.26 has 3 significant figures; 6.1 has 2 significant figures