How to use the fraction reducer and common denominator tool
Enter the numerator and denominator of one fraction and it is reduced to lowest terms. Fill in fraction 2 as well and both are rewritten over the same denominator, with a comparison of which one is larger. Leaving both boxes of fraction 2 blank computes the reduction only, so the tool works either way.
Reducing divides the numerator and denominator by their greatest common divisor. For 12/18 the GCD is 6, so the result is 2/3. The sign is always collected on the numerator: 4/-8 becomes -1/2 and -4/-8 becomes 1/2. Keeping the denominator positive makes rewriting and comparing much simpler. A zero numerator is normalized to a denominator of 1 and displayed as 0.
To find a common denominator, both fractions are reduced first and the least common multiple of the reduced denominators is used. Entering 12/18 and 5/12 gives 2/3 and 5/12, so the common denominator is 12 and the pair becomes 8/12 and 5/12. Only whole numbers are accepted, up to 100000 in absolute value. A zero denominator or a decimal input produces a message. Adding and subtracting fractions is not supported on this page.
Frequently Asked Questions
The numerator and denominator are both divided by their greatest common divisor. For 12/18 the GCD is 6, so the result is 2/3. The GCD used is shown as well.
The sign is always moved to the numerator, so 4/-8 becomes -1/2 and -4/-8 becomes 1/2. Keeping the denominator positive makes comparison and rewriting simpler.
Both fractions are reduced first, then the least common multiple of the reduced denominators is used. For 12/18 and 5/12 that gives 2/3 and 5/12, so the common denominator is 12.