Percent (%) is a ratio that represents parts per hundred. It is one way of expressing a fractional number.


The sales tax in some states is 5%. This amount is equal to 5 cents in sales tax for every 100 cents (or $0.05 per $1.00).

The air we breathe is about 21% oxygen, 78% nitrogen, and 1% argon and other gases. Refer to the image below.

Common fractions and decimal fractions are two other ways of expressing fractional numbers.


Common fraction Decimal fraction Percent
0.1 10%
0.5 50%
1.00 100%
1.25 125%

See also fractional number, ratio.