
Significant Figures

Here are some numbers with their significant figures (S.F.) given and a reason why:
Number  S.F.  Reason 
365  3  All digits from 1 to 9 are significant. 
5005  4  Zero digits are significant when between other numbers. 
0·0012  2  The zeros show the position of the decimal point.
Using standard form, we could write 1·2 × 10^{3}.
This has no leading zeros, but still 2 s.f. 
900  3  The zeros here are part of the number. 
As we shall see, numbers like 900 are sometimes assumed to have 1 s.f. only!
