Cups, Pints, Gallons and Liters: Where Volume Units Come From and Who Uses Them
Volume is the trickiest set of units to convert, because the same name can mean different amounts in different countries. A British pint is about 20% bigger than an American one, and an Australian tablespoon holds a third more than a US one. Here’s how that happened and who uses what.
Need a quick answer? Use the volume converter.
Who uses what today
| Country or context | Everyday volume units |
|---|---|
| Most of the world | Milliliters and liters |
| United States | US fluid ounces, cups, pints, quarts and gallons; gasoline is sold by the US gallon |
| United Kingdom | Liters in shops and at the gas pump, but beer and cider on draught come in imperial pints, and fuel economy is quoted in miles per imperial gallon |
| Ireland | Liters, with beer also sold by the pint |
| Canada | Liters (including gasoline), but recipes often use cups and spoons |
| Australia, New Zealand, South Africa | Liters, plus a metric cup of 250 mL in recipes |
| Oil industry (worldwide) | Barrels of 42 US gallons |
The liter
The liter was one of the original metric units of 1795, defined as the volume of a cube 10 centimeters on each side (a cubic decimeter). For a while it was instead defined as the volume of one kilogram of water, which turned out to be very slightly more than a cubic decimeter. In 1964 it went back to being exactly one cubic decimeter.
Its symbol can be written “l” or “L”. The capital L was officially allowed in 1979 because a lowercase l is easily confused with the number 1.
Why there are two gallons
The word “gallon” comes from the Old Northern French galon, a liquid measure. Medieval England had several gallons at once, depending on what was being measured: wine, ale or grain.
In 1707, England fixed the wine gallon at 231 cubic inches. The American colonies inherited it, and it became the US gallon: exactly 3.785411784 liters.
Britain, though, kept changing. In 1824 the British Weights and Measures Act threw out the old gallons and created a single new one, the imperial gallon, defined as the volume of 10 pounds of water at 62 °F. That made it larger, about 4.546 liters. The United States had been independent for decades by then and never adopted it.
Every unit built from the gallon inherited the split:
| Unit | US | Imperial (UK) |
|---|---|---|
| Gallon | 3.785 L | 4.546 L |
| Quart (¼ gallon) | 946 mL | 1.137 L |
| Pint (⅛ gallon) | 473 mL (16 fl oz) | 568 mL (20 fl oz) |
| Fluid ounce | 29.57 mL | 28.41 mL |
Oddly, a US fluid ounce is slightly bigger than an imperial one, even though the US pint is smaller: the US pint has 16 fluid ounces, while the imperial pint has 20.
Cups and spoons
Cooking measures are the least standard of all:
- US customary cup: 8 US fluid ounces, about 236.6 mL. This is what most American recipes mean.
- US “legal” cup: 240 mL, used on US nutrition labels.
- Metric cup: 250 mL, used in Australia, New Zealand, Canada and South Africa.
- Japanese cup: 200 mL.
Tablespoons vary too. A US tablespoon is about 14.8 mL, and most metric countries use 15 mL, but an Australian tablespoon is 20 mL. A teaspoon is about 5 mL almost everywhere.
For most recipes these differences don’t matter much. For baking, where proportions count, it’s worth knowing which country a recipe comes from, or weighing ingredients instead.
The barrel
A barrel of oil is 42 US gallons, about 159 liters. The size dates back to the early Pennsylvania oil fields of the 1860s, where producers standardized on a 42-gallon barrel, a size already in use for shipping other goods. Oil is still priced and reported in these barrels worldwide, even though it’s now shipped by pipeline and tanker, not in actual barrels.
Quick reference
- 1 US gallon = 4 quarts = 8 pints = 128 fl oz ≈ 3.785 L
- 1 imperial gallon = 8 imperial pints = 160 imperial fl oz ≈ 4.546 L
- 1 US cup ≈ 236.6 mL; 1 metric cup = 250 mL
- 1 US tablespoon = 3 teaspoons ≈ 14.8 mL
- 1 liter ≈ 4.23 US cups ≈ 1.76 imperial pints
Convert any of these with the volume converter.