The GCF of 4 and 8 is 4. The LCM of 4 and 8 is 8.
Factors of 4: 1, 2, 4.
Factors of 8: 1, 2, 4, 8.
Common factors: 1, 2 and 4. The greatest of these is 4.
4 = 2 × 2
8 = 2 × 2 × 2
GCF: multiply the prime factors both numbers share: 2 × 2 = 4.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 2 = 8.
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 4, so GCF(4, 8) = 4.
Multiples of 4: 4, 8, 12, ...
Multiples of 8: 8, 16, ...
The first number in both lists is 8.
4 × 8 = 32 = 4 × 8. This always holds for two numbers, so you can find the LCM as (4 × 8) ÷ 4 = 8.
Divide the top and bottom by the GCF 4: 4/8 = 1/2.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 4 | 2 | 4 |
| 3 and 4 | 1 | 12 |
| 4 and 5 | 1 | 20 |
| 4 and 6 | 2 | 12 |
| 4 and 7 | 1 | 28 |
| 4 and 9 | 1 | 36 |
| 2 and 8 | 2 | 8 |
| 3 and 8 | 1 | 24 |
| 5 and 8 | 1 | 40 |
| 6 and 8 | 2 | 24 |
| 7 and 8 | 1 | 56 |
| 8 and 9 | 1 | 72 |
See also: factors of 4 · factors of 8 · 4/8 as a decimal.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.