Fractions describe parts of a whole: the numerator on top counts the parts you have, and the denominator underneath says how many equal parts make a whole. This calculator works with simple fractions, improper fractions and mixed numbers, and always reduces the answer to lowest terms.
How to use the fraction calculator
- Enter the first fraction. For a mixed number, put the whole part in the left box.
- Pick an operation: add, subtract, multiply or divide.
- Enter the second fraction. The answer appears on the tape as a mixed number, a simplified fraction, a decimal and a percent.
The four fraction rules
Adding and subtracting
Fractions can only be added or subtracted when they share a denominator. Convert each one using the least common denominator (LCD), then combine the numerators:
Multiplying
Multiply straight across — numerator by numerator, denominator by denominator:
Dividing
Multiply the first fraction by the reciprocal of the second:
Simplifying
Divide the numerator and denominator by their greatest common factor (GCF). 18/24 has a GCF of 6, so it reduces to 3/4. A fraction is in lowest terms when the GCF is 1.
Worked example: 2 1/2 − 3/4
- Convert the mixed number: 2 1/2 = (2 × 2 + 1)/2 = 5/2.
- The LCD of 2 and 4 is 4, so 5/2 becomes 10/4.
- Subtract the numerators: 10/4 − 3/4 = 7/4.
- Convert back to a mixed number: 7 ÷ 4 = 1 remainder 3, so the answer is 1 3/4 (1.75).
Where fractions show up in real life
- Cooking: doubling ¾ cup of flour gives 1½ cups; halving it gives ⅜ cup.
- Woodworking and construction: tape measures mark inches in sixteenths, so cuts like 23 5/16″ − 7 3/8″ are everyday fraction subtraction.
- Time: 45 minutes is ¾ of an hour, which is why a time card might show 7.75 hours.
- Money and probability: a 1-in-4 chance is ¼, or 25%.
Common mistakes to avoid
- Adding denominators. 1/2 + 1/3 is not 2/5. Use a common denominator: 3/6 + 2/6 = 5/6.
- Forgetting to flip when dividing. Only the second fraction is inverted.
- Leaving answers unsimplified. Teachers and many answer keys expect lowest terms; the calculator does this for you.
Frequently asked questions
How do you add fractions with different denominators?
Rewrite both fractions over a common denominator — the least common multiple of the two denominators is the tidiest choice — then add the numerators and keep the denominator. Finally simplify. For 3/4 + 5/6 the common denominator is 12, giving 9/12 + 10/12 = 19/12 = 1 7/12.
How do you divide one fraction by another?
Flip the second fraction (take its reciprocal) and multiply. 2/3 ÷ 4/5 becomes 2/3 × 5/4 = 10/12, which simplifies to 5/6.
How do I enter a mixed number?
Type the whole number in the left box and the fraction part in the stacked boxes. For 2 1/2, enter 2, then 1 over 2. Leave the whole-number box empty for a simple fraction.
How do I enter a negative fraction?
Put the minus sign on the whole number for a mixed number (−2 1/2) or on the numerator for a simple fraction (−3/4).
Why is my answer shown as an improper fraction and a mixed number?
Both describe the same value. Improper fractions such as 19/12 are easier to keep calculating with, while mixed numbers such as 1 7/12 are easier to read and measure.