There are 128 fluid ounces in a US gallon. That is 16 cups, 8 pints, 4 quarts or 3.785 liters. Half a gallon is 64 oz, a quarter gallon (a quart) is 32 oz, and 1 oz is 1/128 of a gallon. The UK's imperial gallon is bigger: it holds 160 imperial fluid ounces, about 153.7 US fluid ounces, or 4.546 liters.
The converter above turns any volume — gallons, ounces, cups, pints, quarts, liters, milliliters, spoons or imperial units — into every other unit, in either the US or imperial system, and shows what that much water weighs. Below are gallon and ounce charts, water-bottle counts and the conversions people search for most.
How to use the gallon converter
- Type the amount: whole numbers, decimals or fractions such as 1/2 or 2 1/2.
- Pick the unit you are converting from.
- Choose US or imperial results. Recipes, drinks and fuel in the US use US units; older UK and Canadian sources use imperial.
- Read every unit at once, plus the weight of the same volume of water.
Gallon conversion formula
NIST Handbook 44 defines the US liquid gallon as 231 cubic inches = 128 fluid ounces = 4 quarts = 8 pints, and gives 1 gallon = 3.785 411 784 L. The UK Weights and Measures Act 1985 defines the imperial gallon as 4.546 09 liters, with 8 pints to the gallon and 20 fluid ounces to the pint, so 160 imperial fluid ounces to the gallon.
US fl oz = US gallons × 128andUS gallons = fl oz ÷ 128cups = gallons × 16;quarts = gallons × 4;pints = gallons × 8liters = US gallons × 3.785411784imperial fl oz = imperial gallons × 160;liters = imperial gallons × 4.54609
How many ounces in a gallon
1 US gallon = 128 US fl oz. A US fluid ounce is 29.5735 mL. One imperial gallon = 160 imperial fl oz, and each imperial fluid ounce is slightly smaller (28.4131 mL), but there are more of them, so the imperial gallon is still about 20% bigger.
How many cups in a gallon
1 US gallon = 16 cups. Half a gallon is 8 cups and a quart is 4 cups. Nutrition labels round a cup to 240 mL; the exact US customary cup is 236.59 mL. For cup conversions in recipes, use Cups ↔ mL.
Half a gallon in ounces
½ gallon = 64 fl oz = 8 cups = 2 quarts = 1.893 L. It is a common daily water target: eight 8 oz glasses add up to exactly half a gallon.
How many mL in a gallon
1 US gallon = 3,785.411784 mL (3.785 L). An imperial gallon is 4,546.09 mL. For liters to gallons in both directions, see Liters ↔ Gallons.
Quarts and pints in a gallon
4 quarts or 8 pints. Each US quart is 32 fl oz and each pint 16 fl oz. An imperial pint is 20 imperial fl oz (568.26 mL), which is why a British pint of beer looks larger than an American one.
Gallons to ounces chart
| Gallons | fl oz | Cups | Quarts | Liters |
|---|---|---|---|---|
| 0.125 | 16 | 2 | 0.5 | 0.473 |
| 0.25 | 32 | 4 | 1 | 0.946 |
| 0.333 | 42.67 | 5.33 | 1.33 | 1.262 |
| 0.5 | 64 | 8 | 2 | 1.893 |
| 0.75 | 96 | 12 | 3 | 2.839 |
| 1 | 128 | 16 | 4 | 3.785 |
| 1.5 | 192 | 24 | 6 | 5.678 |
| 2 | 256 | 32 | 8 | 7.571 |
| 2.5 | 320 | 40 | 10 | 9.464 |
| 3 | 384 | 48 | 12 | 11.356 |
| 4 | 512 | 64 | 16 | 15.142 |
| 5 | 640 | 80 | 20 | 18.927 |
| 6 | 768 | 96 | 24 | 22.712 |
| 7 | 896 | 112 | 28 | 26.498 |
| 10 | 1,280 | 160 | 40 | 37.854 |
| 15 | 1,920 | 240 | 60 | 56.781 |
| 20 | 2,560 | 320 | 80 | 75.708 |
| 25 | 3,200 | 400 | 100 | 94.635 |
| 50 | 6,400 | 800 | 200 | 189.271 |
| 55 | 7,040 | 880 | 220 | 208.198 |
| 100 | 12,800 | 1,600 | 400 | 378.541 |
Ounces to gallons chart
| fl oz | Gallons | Cups | mL |
|---|---|---|---|
| 1 | 0.0078 | 0.125 | 29.6 |
| 2 | 0.0156 | 0.25 | 59.1 |
| 4 | 0.0313 | 0.5 | 118.3 |
| 6 | 0.0469 | 0.75 | 177.4 |
| 8 | 0.0625 | 1 | 236.6 |
| 10 | 0.0781 | 1.25 | 295.7 |
| 12 | 0.0938 | 1.5 | 354.9 |
| 16 | 0.125 | 2 | 473.2 |
| 16.9 | 0.132 | 2.113 | 499.8 |
| 20 | 0.1563 | 2.5 | 591.5 |
| 24 | 0.1875 | 3 | 709.8 |
| 25.4 | 0.1984 | 3.175 | 751.2 |
| 32 | 0.25 | 4 | 946.4 |
| 33.8 | 0.2641 | 4.225 | 999.6 |
| 40 | 0.3125 | 5 | 1,182.9 |
| 48 | 0.375 | 6 | 1,419.5 |
| 50 | 0.3906 | 6.25 | 1,478.7 |
| 64 | 0.5 | 8 | 1,892.7 |
| 80 | 0.625 | 10 | 2,365.9 |
| 96 | 0.75 | 12 | 2,839.1 |
| 100 | 0.7813 | 12.5 | 2,957.4 |
| 120 | 0.9375 | 15 | 3,548.8 |
| 128 | 1 | 16 | 3,785.4 |
| 150 | 1.1719 | 18.75 | 4,436 |
| 160 | 1.25 | 20 | 4,731.8 |
| 200 | 1.5625 | 25 | 5,914.7 |
| 256 | 2 | 32 | 7,570.8 |
| 500 | 3.9063 | 62.5 | 14,786.8 |
| 640 | 5 | 80 | 18,927.1 |
| 1,000 | 7.8125 | 125 | 29,573.5 |
US vs imperial gallon
| Unit | US (mL) | Imperial (mL) | Per gallon (US / imp) |
|---|---|---|---|
| Gallon | 3,785.412 | 4,546.09 | 1 / 1 |
| Quart | 946.353 | 1,136.523 | 4 / 4 |
| Pint | 473.176 | 568.261 | 8 / 8 |
| Fluid ounce | 29.5735 | 28.4131 | 128 / 160 |
1 imperial gallon = 1.2009 US gallons; 1 US gallon = 0.8327 imperial gallons. NIST notes the imperial gallon is about 20% larger than the US gallon.
Water bottles and glasses per gallon
Handy if you are tracking water: how many of each container make up a half gallon and a full US gallon.
| Container | Per ½ gallon | Per gallon |
|---|---|---|
| 8 oz glass | 8 | 16 |
| 12 oz can | 5.33 | 10.67 |
| 16 oz bottle | 4 | 8 |
| 16.9 oz (500 mL) bottle | 3.79 | 7.57 |
| 20 oz bottle | 3.2 | 6.4 |
| 24 oz bottle | 2.67 | 5.33 |
| 32 oz bottle | 2 | 4 |
| 40 oz tumbler | 1.6 | 3.2 |
| 1 liter bottle | 1.89 | 3.79 |
Worked examples
A recipe makes 3 quarts of soup
3 × 32 = 96 fl oz, or ¾ gallon (2.84 L).
Filling a 5-gallon water jug from 16.9 oz bottles
5 × 128 = 640 fl oz; 640 ÷ 16.9 = 37.9 bottles. The full jug weighs about 41.7 lb of water.
A UK recipe says 2 pints of milk
2 imperial pints = 38.4 US fl oz = 4.8 US cups, not 4 cups.
Drinking a 40 oz tumbler three times a day
3 × 40 = 120 fl oz = 0.938 gallon, just short of a full gallon.
Common mistakes
- Mixing US and imperial gallons. A UK or Canadian "gallon" in older sources is 160 imperial oz, about 20% more.
- Confusing fluid ounces and weight ounces. A gallon of water holds 128 fl oz of volume but weighs about 133 oz. See Oz ↔ Lbs for weight.
- Using the dry gallon for liquids. Liquids are always liquid gallons.
- Assuming a 1 L bottle is a quart. A liter is 1.057 US quarts, about 6% more.
Related converters
For other volumes see Liters ↔ Gallons, mL ↔ oz and Cups ↔ mL. To weigh a gallon of any liquid, use the weight per gallon calculator.
Frequently asked questions
How many ounces are in a gallon?
128 US fluid ounces are in a US gallon. An imperial (UK) gallon holds 160 imperial fluid ounces, which is about 153.7 US fluid ounces.
How many cups are in a gallon?
16 US cups are in a US gallon (8 fl oz per cup). A quart is 4 cups and a pint is 2 cups.
How many ounces in half a gallon?
Half a US gallon is 64 fl oz, or 8 cups.
How many 16.9 oz bottles make a gallon?
128 ÷ 16.9 = 7.57, so about 7½ standard 500 mL bottles make a gallon.
How many milliliters are in a gallon?
A US gallon is exactly 3,785.411784 mL (about 3.79 L). An imperial gallon is 4,546.09 mL.
How many 8 oz glasses are in a gallon?
16 — the same as cups, since a US cup is 8 fl oz.
How many quarts and pints are in a gallon?
A US gallon is 4 quarts or 8 pints. An imperial gallon is also 4 imperial quarts or 8 imperial pints, but each is about 20% larger.
How many ounces are in a gallon of water by weight?
A US gallon of water weighs about 8.34 lb near 60 °F, which is about 133 ounces of weight — not the same as the 128 fluid ounces of volume.
Is a dry gallon the same as a gallon?
No. The US dry gallon (4 dry quarts, 268.8025 in³) is about 4.405 L, roughly 16% larger than a liquid gallon. It is rarely used; produce is sold by the dry quart, peck or bushel.
How many tablespoons are in a gallon?
256 US tablespoons (16 cups × 16 tablespoons), or 768 teaspoons.
¿Cuántas onzas tiene un galón?
Un galón estadounidense tiene 128 onzas líquidas (16 tazas, 3,785 litros). El galón imperial del Reino Unido tiene 160 onzas imperiales (4,546 litros).
Sources & method
- NIST Handbook 44 (2026), Appendix C: US liquid measure — 16 fl oz = 1 pint; 2 pints = 1 quart; 4 quarts = 1 gallon = 231 in³ = 128 fl oz; 1 gallon = 3.785 411 784 L; dry quart = 67.200 625 in³; the Imperial gallon is divided into 160 fluid ounces
- NIST SP 811, Appendix B.8: gallon (US liquid) = 3.785 412 E−03 m³; gallon [Canadian and UK (Imperial)] = 4.546 09 E−03 m³; fluid ounce (US) = 2.957 353 E−05 m³
- UK Weights and Measures Act 1985, Schedule 1: gallon = 4.546 09 cubic decimetres; quart = 1/4 gallon; pint = 1/8 gallon; fluid ounce = 1/20 pint
- 21 CFR 101.9(b)(5)(viii): for nutrition labeling, 1 cup means 240 mL and 1 fl oz means 30 mL
Results are estimates for general information. Found an error? It helps everyone — see our methodology.