The U.S. liquid gallon is defined as 231 cubic inches, which is 3.785411784 liters. The other U.S. kitchen and liquid units divide it evenly: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces, and 1 fluid ounce = 2 tablespoons = 6 teaspoons. So 5 gallons is 18.93 liters and a 12 fl oz can holds 354.9 mL.
The British (imperial) gallon is larger, exactly 4.54609 L, so watch which one a recipe, fuel figure or product uses. This converter covers both, plus cubic inches, feet and meters for tanks and containers.
How to use the volume converter
- Enter the volume.
- Pick the unit you have and the unit you want.
- Read the result and the table of every unit. For cooking with rounded "metric cup" values, use the cooking converter instead.
Formula
Worked example
Convert 5 US gallons to liters, and 1 cubic foot to gallons.
- 5 × 3.785412 = 18.927 L.
- 1 ft³ = 28.31685 L ÷ 3.785412 L/gal = 7.4805 US gal.
- A 500 mL bottle = 500 ÷ 29.57353 = 16.907 fl oz.
US vs imperial units
| Unit | US | Imperial (UK) |
|---|---|---|
| gallon | 3.785 L | 4.546 L |
| pint | 473.2 mL (16 US fl oz) | 568.3 mL (20 imp fl oz) |
| fluid ounce | 29.57 mL | 28.41 mL |
An imperial gallon is about 1.20 US gallons. This converter's pints, quarts, cups and fluid ounces are U.S. liquid units. For the volume of a pool or a box, start with the pool volume calculator or cubic feet calculator.
Tanks, aquariums and containers
For a box-shaped container, multiply length × width × height to get its volume, then convert. In inches, divide cubic inches by 231 for U.S. gallons (231 in³ = 1 gallon by definition). In feet, multiply cubic feet by 7.48052. In centimeters, divide cubic centimeters by 1,000 for liters (1 L = 1,000 cm³).
Example: a 30 × 12 × 18 inch aquarium holds 6,480 in³ ÷ 231 = 28.05 gallons (106.2 L) when filled to the brim; actual water volume is lower once you allow for gravel and the gap at the top. For pools, the pool volume calculator handles round and oval shapes.
Liquid volume and weight
Volume and weight are different quantities. One liter of water has a mass of about 1 kilogram, so a U.S. gallon of water is about 3.79 kg (8.3 lb), but other liquids are lighter or heavier: oil floats on water because it is less dense, and syrup is denser. Convert between volume and weight only when you know the liquid's density.
Caveats and assumptions
- Pints, quarts, cups and fluid ounces are U.S. customary liquid measures; U.S. dry measures differ.
- For cooking with rounded "metric" measures (cup = 240 or 250 mL), see the cooking converter.
Frequently asked questions
How many liters are in a gallon?
A U.S. gallon is 3.785 liters. An imperial (UK) gallon is 4.546 liters.
How many mL are in a fluid ounce?
A U.S. fluid ounce is 29.57 mL. An imperial fluid ounce is 28.41 mL.
How many cups are in a gallon?
16 U.S. cups (4 quarts, 8 pints, 128 fluid ounces).
How many gallons are in a cubic foot?
About 7.48 U.S. gallons.
How many ounces are in a liter?
About 33.81 U.S. fluid ounces.
How many gallons is 1 liter?
About 0.2642 U.S. gallons.
How many cubic inches are in a gallon?
231 cubic inches in a U.S. liquid gallon.
Sources
- NIST SP 811 Appendix B.9 — Conversion factors — gallon, quart, pint, cup, fluid ounce, tablespoon, teaspoon, cubic inch, cubic foot
- NIST — SI Units: Volume — liter and cubic meter
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.