GCF and LCM of 8 and 13

The GCF of 8 and 13 is 1. The LCM of 8 and 13 is 104.

• GCF (greatest common factor, also called GCD or HCF) of 8 and 13 = 1
• LCM (least common multiple) of 8 and 13 = 104

8 and 13 share no common factor except 1, so they are coprime (relatively prime). When two numbers are coprime their LCM is simply their product: 8 × 13 = 104.

Method 1: list the factors (GCF)

Factors of 8: 1, 2, 4, 8.
Factors of 13: 1, 13.
Common factors: 1. The greatest of these is 1.

Method 2: prime factorization

8 = 2 × 2 × 2
13 = 13 (prime)

GCF: multiply the prime factors both numbers share: there are none, so the GCF is 1.

LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 2 × 13 = 104.

Method 3: Euclidean algorithm (GCF)

Divide the larger number by the smaller and repeat with the remainder until it is 0. The last non-zero remainder is the GCF.

1. 13 = 1 × 8 + 5
2. 8 = 1 × 5 + 3
3. 5 = 1 × 3 + 2
4. 3 = 1 × 2 + 1
5. 2 = 2 × 1 + 0

The last non-zero remainder is 1, so GCF(8, 13) = 1.

LCM by listing multiples

Multiples of 8: 8, 16, 24, 32, 40, 48, 56, 64, 72, ...
Multiples of 13: 13, 26, 39, 52, 65, 78, 91, 104, 117, ...
The first number in both lists is 104.

Check: GCF × LCM = product

1 × 104 = 104 = 8 × 13. This always holds for two numbers, so you can find the LCM as (8 × 13) ÷ 1 = 104.

Simplifying the fraction 8/13

8/13 is already in lowest terms because the GCF of 8 and 13 is 1.

GCF and LCM of similar pairs

See also: factors of 8 · factors of 13 · 8/13 as a decimal.

Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.