There are 16 cups in a gallon of milk. That is the answer: 1 US gallon of milk equals 16 cups, which equals 4 quarts, which equals 8 pints, which equals 128 fluid ounces, which equals 3.79 litres. If a recipe calls for a gallon of milk, you need 16 cups. If you buy a gallon jug and a recipe needs 2 cups, you have used one eighth of the jug. This page gives you the table, real kitchen examples, and the reason the gallon jug is the unit that ties milk together — because milk is sold by the gallon, and the gallon is 16 cups.
The conversion table
| Gallons of milk | Cups | Quarts | Pints | Fluid ounces | Litres |
|---|---|---|---|---|---|
| 1/8 gallon | 2 cups | 1/2 quart | 1 pint | 16 fl oz | 0.47 L |
| 1/4 gallon | 4 cups | 1 quart | 2 pints | 32 fl oz | 0.95 L |
| 1/2 gallon | 8 cups | 2 quarts | 4 pints | 64 fl oz | 1.89 L |
| 3/4 gallon | 12 cups | 3 quarts | 6 pints | 96 fl oz | 2.84 L |
| 1 gallon | 16 cups | 4 quarts | 8 pints | 128 fl oz | 3.79 L |
| 1 1/2 gallons | 24 cups | 6 quarts | 12 pints | 192 fl oz | 5.68 L |
| 2 gallons | 32 cups | 8 quarts | 16 pints | 256 fl oz | 7.57 L |
The litre figures are rounded to two decimal places. A US gallon is 3.785 litres, and a US cup is 236.59 ml, so 3,785 divided by 236.59 is exactly 16.
Worked example 1: a gallon jug and a week of recipes
You buy a gallon of milk on Monday, and your recipes for the week need 2 cups for pancakes on Tuesday, 1 cup for a white sauce on Wednesday, 3 cups for a soup on Thursday, and 2 cups for a cake on Friday. That is 8 cups in total, which is half a gallon, so you will have half a gallon left for cereal and coffee. Knowing that a gallon is 16 cups lets you plan the week: 16 cups minus 8 cups is 8 cups, and you can see at a glance whether the jug will last. If you buy a half-gallon instead, that is 8 cups, and you will run out on Friday, so buy the gallon.
Worked example 2: a large batch of custard for a party
A custard recipe for a party calls for 1 gallon of milk, and your measuring jug holds 4 cups. One gallon is 16 cups, so you need to fill the jug four times. If you are scaling the recipe down for a family dinner, you need a quarter of a gallon, which is 4 cups, or 1 quart, and that is a single jugful. The gallon-to-cup conversion is most useful at this scale, where you are portioning and scaling rather than measuring for a single meal, and where a mistake means a custard that is too thin or too thick.
Worked example 3: a gallon of milk and its weight
A gallon of milk weighs about 8.6 pounds, or 3.9 kilograms, which is slightly more than a gallon of water, because milk is denser than water. That matters if you are carrying it, or if a recipe gives a weight rather than a volume: 16 cups of milk is 3,840 grams, because a cup of milk weighs about 240 grams. If a European recipe calls for 4 litres of milk, that is 16.9 US cups, which is a little more than a gallon, so you need a gallon plus about a cup. The weight is a useful check: if you weigh the jug and it reads 8.6 pounds, you have a full gallon.
Method and source
A US gallon is defined as 231 cubic inches, which is 3.785 litres. A US cup is 8 fluid ounces, or 236.59 millilitres, and 3,785 divided by 236.59 is exactly 16. The American system is built on powers of two, so the gallon chain is clean: 16 cups, 8 pints, 4 quarts, 1 gallon. Milk is sold by the gallon in the United States because the gallon is the standard unit for liquids, and a gallon jug is the most common size. In Britain, milk is sold by the litre and the pint, so a "gallon of milk" in a British recipe usually means 4.55 litres, which is 19.2 US cups, and that is the difference to watch for.
Practical guidance
Learn the chain: 1 gallon is 4 quarts, 1 quart is 2 pints, 1 pint is 2 cups. If you know that, you can convert a gallon to cups by multiplying by 16, to quarts by multiplying by 4, and to pints by multiplying by 8. When you are scaling a recipe, convert to cups first, because cups are the smallest unit and the maths stays in whole numbers. Store milk in the fridge, in its jug, and use it within a week of opening — or by the date printed on the jug, whichever comes first. And when a recipe calls for milk by weight, remember that a cup of milk weighs about 240 grams, so 16 cups is about 3,840 grams.
Frequently asked questions
How many cups are in a gallon of milk?
There are 16 cups in a gallon of milk. That is the standard American conversion, and it is the same for any liquid. A gallon jug of milk holds 16 cups, which is why it is useful to know.
How many cups are in half a gallon of milk?
There are 8 cups in half a gallon of milk. Half a gallon is also 2 quarts, 4 pints, 64 fluid ounces, and about 1.89 litres. A half-gallon carton of milk holds 8 cups.
How many quarts are in a gallon of milk?
There are 4 quarts in a gallon of milk. Four quarts is also 8 pints, 16 cups, and 128 fluid ounces. A quart carton of milk holds 4 cups.
How much does a gallon of milk weigh?
A gallon of milk weighs about 8.6 pounds, or 3.9 kilograms. That is slightly more than a gallon of water, which weighs 8.34 pounds, because milk is denser than water. A cup of milk weighs about 240 grams.
How many cups are in a litre of milk?
There are 4.23 US cups in a litre of milk, and 4 metric cups in a litre. A litre is slightly larger than a quart, which holds 4 cups, so a litre carton holds 4 cups plus about a quarter of a cup.
How long does a gallon of milk last?
Usually 5 to 7 days after opening, or until the date printed on the jug, whichever comes first. Store it in the fridge, not in the door, where the temperature fluctuates, and do not leave it out at room temperature for more than two hours.
A gallon of milk is 16 cups, which is more than most recipes ever need at once. Once opened, it keeps for about a week in the fridge, and it freezes well in smaller containers for later baking — thaw it in the fridge overnight and shake it well, because the fat separates as it freezes and needs mixing back in.