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The detailed guide below is currently available in English.
Two ways to enter a fraction
The Fractions tab gives each fraction two boxes: a numerator on top and a denominator underneath — leave nothing else to fill in. The Mixed Numbers tab takes a single value per fraction, so you can type a mixed number the way it is read aloud: 3 5/7 means three and five-sevenths. A leading minus sign makes the whole value negative, so -2 3/4 equals −11/4 as an improper fraction, and plain entries like 5/8 or 4 work there too.
How addition and subtraction work
Both fractions are first rewritten as improper fractions. To add or subtract, the calculator finds the least common denominator (LCD) of the two denominators, rescales each numerator to that LCD, then adds or subtracts the numerators. For example 1/2 + 1/3 becomes 3/6 + 2/6 = 5/6 with an LCD of 6. The result is reduced by dividing out the greatest common divisor, so you never see 4/8 when 1/2 is the same value.
How multiplication and division work
Multiplication needs no common denominator: multiply the two numerators, multiply the two denominators, and simplify. Division uses the reciprocal trick — flip the second fraction and multiply, so 1/2 ÷ 3/4 becomes 1/2 × 4/3 = 4/6, which simplifies to 2/3. Dividing by a fraction that equals zero is undefined, and the calculator stops you with a friendly message instead of a broken answer.
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How do I enter a negative fraction?
Put the minus sign in front of the value: in the Fractions tab make the numerator negative, and in the Mixed Numbers tab type -2 3/4 with the sign on the front. Both forms are converted to improper fractions before calculating.
Why is my answer an improper fraction?
The headline shows the simplified exact fraction, which may be improper (numerator larger than the denominator). The rows underneath always give the mixed-number form and the decimal form, so you can read the value whichever way you prefer.
What can I type in the mixed-number boxes?
A mixed number like 3 5/7, a simple fraction like 5/8, or a whole number like 4 — each with an optional leading minus sign. Decimals such as 0.25 are not accepted; type 1/4 instead.