The GCF of 6 and 18 is 6. The LCM of 6 and 18 is 18.
Factors of 6: 1, 2, 3, 6.
Factors of 18: 1, 2, 3, 6, 9, 18.
Common factors: 1, 2, 3 and 6. The greatest of these is 6.
6 = 2 × 3
18 = 2 × 3 × 3
GCF: multiply the prime factors both numbers share: 2 × 3 = 6.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 3 × 3 = 18.
Divide the larger number by the smaller and repeat with the remainder until it is 0. The last non-zero remainder is the GCF.
The last non-zero remainder is 6, so GCF(6, 18) = 6.
Multiples of 6: 6, 12, 18, 24, ...
Multiples of 18: 18, 36, ...
The first number in both lists is 18.
6 × 18 = 108 = 6 × 18. This always holds for two numbers, so you can find the LCM as (6 × 18) ÷ 6 = 18.
Divide the top and bottom by the GCF 6: 6/18 = 1/3.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 6 | 2 | 6 |
| 3 and 6 | 3 | 6 |
| 4 and 6 | 2 | 12 |
| 5 and 6 | 1 | 30 |
| 6 and 7 | 1 | 42 |
| 6 and 8 | 2 | 24 |
| 2 and 18 | 2 | 18 |
| 3 and 18 | 3 | 18 |
| 4 and 18 | 2 | 36 |
| 5 and 18 | 1 | 90 |
| 7 and 18 | 1 | 126 |
| 8 and 18 | 2 | 72 |
See also: factors of 6 · factors of 18 · 6/18 as a decimal.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.