RULES 
(Significant
figures are the figures in red) 
Rule 1. All nonzero
integers are significant. 
eg  456 cm 
456
cm
has 3 significant figures

Rule 2. All zeros to the
left of the first nonzero digit are not significant since they are used
to locate the decimal point. 
eg  0.00567 kg 
0.00567
kg
has 3 significant figures

Rule 3. All zeros between nonzero digits
are significant. 
eg 1  207.08 cm 
207.08 cm
has 5 significant figures 

eg 2  0.0401 L 
0.0401 L
has 3 significant figures 
Rule 4. All zeros at the end of a number
that has a decimal point are significant. 
eg 1  34.070 mg

34.070 mg
has 5 significant figures


eg 2  0.0670 g 
0.0670 g
has 3 significant figures 

eg 3  400. mm 
400. mm
has 3 significant figures 
Rule 5. Zeros at the
end of a whole number that has no decimal point
is confusing since they may or may not be
significant. 
eg  300 L 
???????
The measurement, "300 L", as written is confusing. 