How to use it
- Type an amount. Commas, decimals and scientific notation all work.
- Choose units. US units (US cup, US gal) and imperial units (imp pt, imp gal) are listed separately, because they are different sizes.
- Read the vessel: metric marks on the left, US or imperial marks on the right, on one shared scale.
How the conversion works
The US gallon is defined as exactly 231 cubic inches, and the imperial gallon as exactly 4.54609 liters. Everything else divides from them:
1 US gal = 231 in³ = 3.785411784 L (exact)
1 US gal = 4 qt = 8 pt = 16 cups = 128 US fl oz
1 US fl oz = 29.5735295625 mL; 1 US cup = 236.5882365 mL (exact)
1 tbsp = 3 tsp = ½ US fl oz
1 imp gal = 4.54609 L = 160 imp fl oz (exact)
US nutrition labels use a rounded “legal cup” of 240 mL, and many metric recipes use a 250 mL cup. This converter uses the customary US cup (236.588 mL) and says so in the unit name.
Worked examples
1 US cup in milliliters
8 × 29.5735295625
236.5882365 mL
2 liters in US gallons
2 ÷ 3.785411784
0.5283 US gal
1 imperial gallon in US gallons
4.54609 ÷ 3.785411784
1.2009 US gal
16 US fl oz in milliliters
16 × 29.5735295625
473.176473 mL
1 tablespoon in teaspoons
1 × 3
3 tsp
1 cubic foot in liters
1,728 × 0.016387064
28.32 L
US or imperial?
The United States kept the older wine gallon (231 in³), while the UK redefined its gallon in 1824. As a result, an imperial gallon, quart and pint are about 20% larger than their US namesakes, but an imperial fluid ounce is about 4% smaller than a US fluid ounce. If a recipe or fuel figure comes from the UK, Canada (older recipes) or Australia (older recipes), it probably uses imperial sizes.
Where this comes up
- Cooking: cups and spoons in US recipes, milliliters and grams elsewhere.
- Drinks: 12 fl oz cans, 750 mL bottles, 2-liter sodas.
- Fuel and fluids: gallons at US pumps, liters almost everywhere else.
- Storage and shipping: cubic feet and cubic meters.
Accuracy and rounding
Every factor here is exact; results are rounded only for display. Container sizes used for comparison (a can, a wine bottle, a drum, a pool) are nominal sizes.
Questions
How many liters are in a gallon?
A US gallon is exactly 3.785411784 liters. An imperial (UK) gallon is exactly 4.54609 liters.
How many cups are in a liter?
About 4.2268 US cups (1 ÷ 0.2365882365).
How many fluid ounces are in a cup?
A US cup is exactly 8 US fluid ounces.
Is a fluid ounce the same as an ounce?
No. A fluid ounce measures volume; an ounce measures weight. One US fluid ounce of water weighs about 1.04 oz.