How it works
A fraction is a division problem: 3/8 means 3 ÷ 8 = 0.375. Multiply the decimal by 100 to get the percent, 37.5%.
A fraction in lowest terms terminates only when its denominator has no prime factors other than 2 and 5. Anything else repeats forever; the repeating block is shown in parentheses, so 1/7 appears as 0.(142857).
Formula
decimal = numerator ÷ denominator; percent = decimal × 100
Questions people ask
Which fractions give terminating decimals?
Those whose reduced denominator factors only into 2s and 5s, such as 1/4, 3/8, 7/20 or 9/125. Denominators like 3, 6, 7, 9 or 11 always repeat.
How long can the repeating block be?
For a denominator d, the block has at most d − 1 digits. 1/7 repeats every 6 digits and 1/17 every 16.
What does 0.1(6) mean?
It means 0.16666…, where only the 6 repeats. That is the decimal form of 1/6.