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Subtracting Fractions Calculator

Type the value you are subtracting from into the First fraction field and the value to take away into the Second fraction field, then press = to see the difference in cards below the button.

What this calculator does

The form has two text fields, First fraction and Second fraction. Type a value into each one and then press the = button — nothing is worked out until you press it. The answer appears in cards below the button.

Each field takes a simple fraction such as 1/2, a mixed number such as 2 1/2, or a whole number such as 3. The difference comes back as a fraction and as a decimal, and as a mixed number too when the top of the fraction is bigger than the bottom.

Taking a bigger value from a smaller one gives a negative difference, and taking a value from the same value leaves nothing: 1/2 - 1/2 = 0/1 = 0. Copy writes a result and its unit to the clipboard; Clear resets the form so you can try another pair.

Subtracting fractions formula

When the two bottom numbers are already the same, only the top numbers are subtracted and that bottom number is kept: 3/4 - 1/4 = 1/2 = 0.5.

When the bottom numbers differ, both fractions are rewritten over one shared bottom number before the top numbers are subtracted: 1/2 - 1/3 = 1/6 = 0.166667.

Mixed numbers and whole numbers are handled the same way: 2 1/2 - 1 1/3 = 7/6 = 1 1/6 = 1.166667 and 3 - 1/2 = 5/2 = 2 1/2 = 2.5.