Fraction Calculator
Simplify a fraction to lowest terms, or add, subtract, multiply and divide two fractions. Every answer is reduced and shown with its decimal value.
Last updated: October 2026
Answer (lowest terms)
2/3 (= 0.666667)
Formula below · 2 sources (khanacademy.org, mathworld.wolfram.com) · Updated Oct 2026
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About this calculator
A fraction is in lowest terms when the numerator and denominator have no common factor except 1. To simplify, divide both by their greatest common factor (GCF): the GCF of 12 and 18 is 6, so 12/18 = 2/3. The calculator finds the GCF with Euclid's algorithm and reduces every answer this way.
The four operations
Add or subtract: put both fractions over a common denominator, then add or subtract the numerators. a/b + c/d = (a·d + c·b) / (b·d). For 1/2 + 1/3 that is (3 + 2)/6 = 5/6.
Multiply: multiply the numerators and the denominators. a/b × c/d = (a·c)/(b·d), so 2/3 × 3/4 = 6/12 = 1/2.
Divide: multiply by the reciprocal of the second fraction. a/b ÷ c/d = (a·d)/(b·c), so 3/4 ÷ 1/2 = 6/4 = 3/2.
Signs, whole numbers and mixed numbers
A negative sign can go on either number; the answer always carries it on the numerator (5/−10 = −1/2). Enter a whole number as a fraction over 1 (3 = 3/1). Convert a mixed number to an improper fraction first: 2 1/4 = (2 × 4 + 1)/4 = 9/4. An improper answer such as 7/3 equals 2 1/3 (7 ÷ 3 = 2 remainder 1). A denominator of 0 has no meaning, so the calculator reports it as undefined.
| Operation | Rule | Example |
|---|---|---|
| Simplify | Divide top and bottom by their GCF | 12/18 = 2/3 |
| Add | (a·d + c·b) / (b·d) | 1/2 + 1/3 = 5/6 |
| Subtract | (a·d − c·b) / (b·d) | 3/4 − 1/6 = 7/12 |
| Multiply | (a·c) / (b·d) | 2/3 × 3/4 = 1/2 |
| Divide | (a·d) / (b·c) | 3/4 ÷ 1/2 = 3/2 |
How to use
Enter the first fraction, pick an operation, and enter the second fraction if the operation needs one. Simplify (the default): 12/18 gives 2/3 (= 0.666667), because both numbers divide by 6. Add: 1/2 + 1/3 gives 5/6 (= 0.833333). Subtract: 3/4 − 1/6 gives 7/12 (= 0.583333), using the common denominator 24 and then reducing 14/24. Multiply: 2/3 × 3/4 gives 1/2 (= 0.5). Divide: 3/4 ÷ 1/2 gives 3/2 (= 1.5), which is 1 1/2 as a mixed number.
Frequently asked questions
How do you simplify a fraction?
Divide the numerator and denominator by their greatest common factor. For 18/24 the GCF is 6, so 18/24 = 3/4. If the GCF is 1 the fraction is already in lowest terms.
How do you add fractions with different denominators?
Rewrite both over a common denominator, add the numerators, then simplify. 1/4 + 1/6: the least common denominator is 12, so 3/12 + 2/12 = 5/12. Multiplying the two denominators (24) also works; you just simplify more at the end.
How do you divide fractions?
Flip the second fraction and multiply. 2/5 ÷ 3/4 = 2/5 × 4/3 = 8/15. You cannot divide by a fraction whose numerator is 0, because that fraction equals zero.
How do I enter a mixed number like 1 1/2?
Convert it to an improper fraction first: multiply the whole number by the denominator and add the numerator. 1 1/2 = (1 × 2 + 1)/2 = 3/2. Enter 3 as the numerator and 2 as the denominator.
What does an improper answer like 7/3 mean?
The numerator is larger than the denominator, so the value is more than 1. Divide to get the mixed number: 7 ÷ 3 = 2 remainder 1, so 7/3 = 2 1/3. The decimal in brackets (2.333333) shows the same value.
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