How Many Cups Are in a Gallon of Water?
16 cups
A US gallon holds 128 fluid ounces, which is 16 cups of 8 fl oz each. NIST lists the same gallon as 4 quarts.
A UK (imperial) gallon is bigger: 160 imp fl oz, or about 19.2 US cups.
A gallon of water in cups, quarts, pints and liters
| Measure | US gallon | UK gallon |
|---|---|---|
| US cups | 16 | 19.2 |
| US fluid ounces | 128 | 153.7 |
| Imperial fluid ounces | 133.2 | 160 |
| Quarts (same system as the gallon) | 4 | 4 |
| Pints (same system as the gallon) | 8 | 8 |
| Liters | 3.785 | 4.546 |
| US gallons | 1 | 1.201 |
How to measure a gallon of water with cups
A one-cup measure works, but it takes a lot of refills. A quart-size measuring pitcher, which holds 4 cups, is faster: fill it 4 times. With a two-cup measure, you need 8 fills.
You can also weigh the water. Based on USDA data, water weighs about 237 grams per cup, so a full gallon comes to about 8.35 pounds without the container. The gallons to pounds converter works out other amounts.
Is a UK gallon the same as a US gallon?
No, the UK gallon is bigger. UK law sets the imperial gallon at exactly 4.54609 liters, which is 1.201 US gallons.
An imperial gallon holds 160 imp fl oz. That is 8 imperial pints of 20 imp fl oz each, and every imperial pint is 568.26 ml. A US pint holds only 473.18 ml.
So a British gallon of water fills about 19.2 US cups instead of 16. The gallons to cups converter lets you switch between the two systems.
What do health agencies say about cups of water a day?
There is no single official number of cups. When the National Academies set water intake levels in 2004, the panel said it offered no rule of thumb for how many glasses to drink each day.
Its figures are for total water from all drinks and food. Women who appeared well hydrated took in about 2.7 liters a day on average, and men about 3.7 liters. About 80% of that total came from water and other drinks, including drinks with caffeine.
In the UK, the NHS says to aim for six to eight cups or glasses of fluid a day. It talks about fluid in general, not only water.
The CDC notes that daily water recommendations vary by age, sex, pregnancy, activity level and breastfeeding. For an estimate based on your own details, try the water intake calculator.
How many glasses and bottles make a gallon?
Divide 128 fl oz by the size of the glass or bottle. The table below does the math for a few sizes you may have at home.
A two-liter bottle is a little more than half a gallon, so two of them hold more than a gallon. For bottled water sizes by brand, see how many ounces are in a water bottle.
| Glass or bottle | Number in a US gallon |
|---|---|
| 8 fl oz glass (one cup) | 16 |
| 12 fl oz glass | 10.7 |
| 16 fl oz glass or bottle | 8 |
| 500 ml bottle | 7.6 |
| 1 L bottle | 3.8 |
| Two-liter bottle | 1.9 |
Gallon of water: questions
Is 128 oz the same as 1 gallon?
Yes. NIST Handbook 44 lists the US gallon as exactly 128 fluid ounces. A UK gallon is different: it holds 160 imp fl oz, and each imperial ounce is a little smaller than a US one.
Is 64 oz of water 1 gallon?
No, 64 fl oz is half a US gallon. It equals 8 cups or 2 quarts, so you need two of those amounts to make a full gallon.
How many 8 oz glasses of water are in one gallon?
A gallon fills 16 glasses of 8 fl oz, because each one holds exactly one US cup. With bigger 12 fl oz glasses, you get about 10.7.
How many 16 oz bottles of water make a gallon?
It takes 8 bottles or glasses of 16 fl oz to make a US gallon. Bottles of 500 ml hold a little more, 16.9 fl oz, so about 7.6 of them fill a gallon.
Is drinking 1 gallon of water a day a lot?
A gallon, 128 fl oz, is more than the average total intake the National Academies reported: about 91 fl oz for women and 125 fl oz for men, counting food and all drinks. Needs vary from person to person, as the CDC notes, so use the calculator for an estimate.
Related
Sources
- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement, checked
- NIST, Metric Kitchen: Cooking Measurement Equivalencies, checked
- Weights and Measures Act 1985, Schedule 1 (legislation.gov.uk), checked
- National Academies of Sciences, Engineering, and Medicine, Report Sets Dietary Intake Levels for Water, Salt, and Potassium (2004), checked
- NHS, Water, drinks and your health, checked
- Centers for Disease Control and Prevention (CDC), Water and Healthier Drinks, checked
Sources: Unit definitions: NIST Handbook 44 · Last reviewed · Report an error
https://howmanyounces.com/how-many-cups-in-a-gallon-of-water/