Add or subtract two fractions, then see the simplified result.
Last updated: June 2026 | By Patchworkr Team
Addition combines two fractional parts into one total. Subtraction removes one fractional part from another.
Both operations use the same basic setup: rewrite the fractions so they share the same denominator, then combine the numerators.
In a fraction, the numerator is the top number and the denominator is the bottom number.
Equivalent fractions have different-looking numerators and denominators, but they represent the same value.
Common denominators work because they turn the fractions into equivalent fractions with the same-sized parts.
If the denominators already match, add or subtract the numerators directly.
When the denominators are different, you must rewrite the fractions using a shared denominator before combining them.
Common denominators let you compare like-sized parts. That is why the arithmetic happens on the numerators after the fractions are rewritten.
For example, 1/2 and 1/3 become 3/6 and 2/6. Those fractions now describe the same-sized parts, so they can be added or subtracted directly.
The least common denominator is usually the cleanest choice because it keeps the numbers smaller and makes simplification easier afterward.
A positive result means the first fraction is larger after combining the values.
A negative result means the second fraction is larger, which can happen in subtraction.
A zero result means the fractions cancel each other out completely.
If you subtract 1/3 from 1/2, the common denominator is 6.
The calculator shows the simplified fraction and a decimal approximation so you can read the result in either format.
Why do I need a common denominator?
You can only add or subtract like quantities.
Can the result be negative?
Yes, subtraction can produce a negative fraction.
Does it simplify automatically?
Yes. The result is always reduced to lowest terms.
Can I switch between add and subtract?
Yes. Use the toggle above the result panel.
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