

Each fraction can be reduced to itâ€™s simplest form, in which the numerator and denominator are as small as possible. To simplify a fraction you have to find the greatest common factor (GCF) of the numerator and denominator. A common factor is a number through which both numerator and denominator can be divided. By dividing both numerator and denominator by the GCF, your fraction is reduced to it's simplest form.
Often you can find the GCF by trial and error. But there is also a method to find the GCF. Therefore we use use prime numbers. A prime number is a number that is divisible only by itself and 1:
The list of prime numbers is infinite: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 39, 41, 43, 47, 53, etc.
In order to simplify 5/10 we write both numerator and denominator as a product of only prime numbers (each number can be written as a product of only prime numbers). This method is called prime factorization:
5  =  5 x 1  =  1 
10  2 x 5  2 
The GCF is the product of the common primes (crossed out above) in the numerator and denominator:
GCF = 5
Check whether you have the simplest form of the fraction and see if you have the numerator and denominator as small as possible. Fill in the numerator above the scoreline and the denominator below the scoreline and click "Simplify fraction" to make the calculation. The simplify fractions calculator shows the fraction in its simplest form and shows the Greatest Common Factor (GCF).