Download Significant Figures: Rules for What Digits Count as Significant (*note

Significant Figures: Rules for What Digits Count as Significant (*note—for
measurements only)
**NOTE: Exact numbers obtained from counting, numerical definitions or equivalents (60 seconds = 1
hour, 1kg = 1,000g, 10 eggs) are considered to have infinite significant figures.**
Number
Digits to Count
Example
Significant Figures
No zeros
All digits
13534
5
Leading Zeros (to the
left)
Captive Zeros
None of the zeros, All
non-zeros digits
All digits
0.00045
2
12004
5
Trailing Zeros (to the
right)
Count all non-zero digits 400.0 and 400 and 400.
and trailing zeros WHEN and 0.040
DECIMAL PRESENT. Do
not count if no decimal
point
All digits in front of x10 3.710 x 107
2.040 x 10-2
Scientific Notation
4 and 1 and 3 and 2
3
4 (from 0.02040)
Rules for Use of Significant Figures in Calculations
In multiplication and division: answers must be the same as the least number of significant figures used
in the calculation.
Example: 234.75 grams x 24.1 grams
Note the first number has 5 sig figs and the second number has 3 sig figs. The answer must be the same
as the least number of sig figs used in the calculation (3).
the raw calculation shows 5,657.475 grams (not correct for sig figs)
Correct Answer: 5,660 grams (rounding to three, correct sig figs )
In addition and subtraction: answers must be the same as the least number of decimal places
regardless of the total number of significant figures of each number.
Example: 41.273 + 10,034.2
Note the first number has 3 digits after the decimal point, the second number has 1 number after the
decimal point. Following the rules, the answer must be the same as the least number of decimal places
after the decimal point.
Correct Answer: 10,075.5 (10,075.473 rounded up to one place after the decimal)