Download Rules for significant figures

Significant Figures
Significant figures are those digits in a measurement that are known with certainty
plus the first digit that is uncertain.
Example 156.3 cm has 4 significant figures.
Rules for significant figures
(1) All non-zero figures are significant. 115.32 kg has 5 significant figures.
(2) All zeros between non-zero digits are significant. 22004 g has 5 significant
figures.
(3) Zeros to the right of a non-zero figures, but to the left of an understood decimal
point, are not significant unless specifically indicated to be significant by the use
of a bar over a zero. 93000 seconds has 2 significant figures.
(4) All zeros to the right of a decimal point but to the left of a non-zero figure are not
significant. 0.00002243 km has 4 significant figures.
(5) All zeros to the right of a decimal point and following a non-zero figure are
significant. 0.020400 ml has 5 significant figures.
(6) In addition or subtraction, the sum or difference has significant figures only in the
decimal places where both of the original numbers had significant figures.
5.2
+ 3.1
8.3
6.843
+ 1.2
8.0
6.843
+1
8
6.843
- 0.001
6.842
(7) In multiplication and division, the product or quotient cannot have more
significant figures than there are in the least accurately known of the original
number. That is, count the significant figures in each of the number being
multiplied or divided and keep the least amount for the number of significant
figures for the solution.
5.2 x 3.1 = 16
5.243 x 3.1 = 16
(8) When rounding off, if the first number to be dropped is:
4 or less  round down
6 or greater  round up
5 followed by non-zero numbers  round up
exactly 5  round to the nearest even number.