Divide by four — the ratio is exact
gallons = quarts ÷ 4, quarts = gallons × 4
A quart is a quarter of a gallon, so this is a clean division, not an approximation. The whole US liquid ladder follows from it: 1 gal = 4 qt = 8 pints = 16 cups = 128 fl oz.
Quick reference
| Quarts | Gallons | Everyday amount |
|---|---|---|
| 1 qt | 0.25 gal | Small carton |
| 2 qt | 0.5 gal | Half-gallon of milk |
| 3 qt | 0.75 gal | — |
| 4 qt | 1 gal | One gallon |
| 5 qt | 1.25 gal | 4-cylinder oil change |
| 6 qt | 1.5 gal | Large stockpot |
| 8 qt | 2 gal | — |
| 20 qt | 5 gal | 5-gallon bucket |
Where the number goes wrong
- US vs Imperial. The 4-to-1 ratio is identical, but the units are not the same size. A US gallon is 3.785 L; an Imperial gallon is 4.546 L, about 20% bigger. Convert quarts to gallons within one system, then translate between systems if you need to.
- Dry vs liquid quart. The US dry quart (1,101 mL) is 16% larger than the liquid quart (946 mL). Berries and produce are sometimes sold by the dry quart; everything else here is liquid.
- A quart is not a liter. 1 US quart is 0.946 L, so it runs about 5% short of a liter. Close for a rough estimate, not for a recipe that has to balance.
Common questions
How many quarts are in a gallon?
Exactly 4. That holds in both the US and the Imperial system, because a quart is defined as a quarter of a gallon. So 2 gallons is 8 quarts and 5 gallons is 20 quarts.
Is 2 quarts half a gallon?
Yes. 2 quarts is exactly 0.5 gallon. A half-gallon carton of milk holds 2 quarts.
How many gallons is 5 quarts of oil?
1.25 gallons. This trips people up at the parts counter: a 5-quart oil change is not one gallon, it is a gallon plus one more quart.
