Why is the answer always reduced?

Because an unreduced fraction is the same number written less clearly, and reducing is the step people most often want anyway. The divisor used is shown, so you can see what came out.

How is a negative fraction written?

With the sign on the numerator. A denominator of minus four is the same number written confusingly, so it is normalised: minus three over four rather than three over minus four.

Why can I not use decimals in a fraction?

Because a fraction is a ratio of whole numbers by definition, and 1.5 over 2 is really 3 over 4 written awkwardly. Convert first, or use the ratio calculator, which does take decimals.

Fraction Calculator

Fractions, reduced, with the decimal shown.

Operation

First numerator

First denominator

Second numerator

Second denominator

Fractions, reduced, with the decimal shown.

How to use it

Pick the operation. Simplify and To a decimal use only the first fraction.
Enter the fractions. Whole numbers above and below. A denominator of zero is refused.
Read all three forms. The reduced fraction, the decimal and the percentage.

When you would use this

Fraction arithmetic is the sort of thing everyone learned and few people do often enough to stay quick at, and the tedious part is not the arithmetic but the reducing at the end. Every answer here comes back in its lowest terms, with the divisor it used shown alongside, plus the decimal and the percentage. Those three forms answer three different questions and it costs nothing to give all of them. Signs are normalised onto the numerator. Minus three over four and three over minus four are the same number, and only one of them is how anyone writes it. Division inverts and multiplies, which is where a zero in the wrong place stops being arithmetic: dividing by a fraction whose numerator is zero has no answer, so it is refused rather than producing an infinity. Fractions are made of whole numbers by definition, so decimals are refused with an explanation rather than being silently rounded. The ratio calculator takes decimals if that is what you have.

Questions

Why is the answer always reduced?: Because an unreduced fraction is the same number written less clearly, and reducing is the step people most often want anyway. The divisor used is shown, so you can see what came out.
How is a negative fraction written?: With the sign on the numerator. A denominator of minus four is the same number written confusingly, so it is normalised: minus three over four rather than three over minus four.
Why can I not use decimals in a fraction?: Because a fraction is a ratio of whole numbers by definition, and 1.5 over 2 is really 3 over 4 written awkwardly. Convert first, or use the ratio calculator, which does take decimals.