Fraction of a number

What it's for

«Three quarters of 240», «two fifths of the salary», «half a recipe, for two instead of four»: they're all the same question, how much a part of a whole is worth. Here you type the fraction and the number and the sum is done. It's useful in the kitchen, at school, on a building site when material gets divided, and every time a share is written as a fraction instead of a percentage.

How it's worked out

You divide the number by the denominator and multiply by the numerator. In practice: first make one part, then take as many as you need. Three quarters of 240 is 240 ÷ 4 = 60, and 60 × 3 = 180. The order can be swapped (240 × 3 = 720, divided by 4 = 180) and the result is the same, but dividing first keeps the numbers small and is easier in your head.

«A third of» and «a third less» are not the same thing

It's the commonest mix-up, and it changes the result a great deal. A third of 90 is 30; 90 with a third less is 60, that is two thirds. When a discount or a cut is written as a fraction («a quarter less») what you need isn't the fraction, but what's left: three quarters.

Fractions and percentages say the same thing

A fraction is a percentage written another way: 1/2 is 50%, 1/4 is 25%, 3/4 is 75%, 1/3 is 33.3%, 2/3 is 66.7%. Fractions are handier when the parts are few and equal (half, a quarter, a third); percentages when different things have to be compared. The step from one to the other is done by Fraction to decimal.

Nearby tools

For the opposite direction, from decimal to fraction, there is Decimal to fraction; for percentages Percentage calculator. In the kitchen, to rework a recipe for a different number of people, the right page is Servings per person, and to change the tin size Cake servings.