½ How to Add, Subtract, Multiply and Divide Fractions

Each fraction operation has its own rule, and mixing them up is the most common source of fraction mistakes — multiplying when you should find a common denominator, or forgetting to flip the second fraction when dividing.

Adding and Subtracting: Common Denominator First

Fractions can only be added or subtracted directly when they share the same denominator. If they don't, convert both to an equivalent fraction with a shared denominator first — typically the least common multiple of the two denominators — then add or subtract the numerators, keeping the denominator unchanged.

Multiplying: No Common Denominator Needed

Multiplication is the simplest operation — multiply the numerators together, multiply the denominators together, no common denominator required at all: (a/b) × (c/d) = (a×c)/(b×d).

Dividing: Flip and Multiply

Dividing by a fraction is the same as multiplying by its reciprocal (flip the numerator and denominator, then multiply): (a/b) ÷ (c/d) = (a/b) × (d/c).

Simplifying the Result

A fraction is fully simplified when the numerator and denominator share no common factors — dividing both by their greatest common divisor (GCD) gets you there. 6/15 and 2/5 represent the same value, but 2/5 is the simplified form.

Step-by-Step: Calculate With Fractions

1. Enter your two fractions
2. Choose the operation: add, subtract, multiply, or divide
3. Get the result already simplified, plus its decimal equivalent