Volume Unit Converter
Convert between milliliter, liter, cubic meter, US gallon, UK gallon and cubic foot.
Volume Conversion: US and Imperial Gallons Differ by 20%
The biggest trap: there are two gallons
| Unit | Liters | Region |
|---|---|---|
| US gallon | 3.785411784 L | United States |
| Imperial gallon | 4.54609 L | Historic UK; some Commonwealth countries still use it for fuel and beer |
| Difference | ≈ 20% | — |
The same word "gallon" differs by 20% — the largest gap in any unit family here. Whenever you see "gallon" you must confirm US or imperial, especially for fuel economy (mpg), tank capacity, paint quantities, and keg sizes. UK fuel figures use the imperial gallon; comparing them directly against US data yields wrong conclusions.
Fluid ounces also split in two
| Unit | Milliliters | Note |
|---|---|---|
| US fluid ounce | 29.5735295625 mL | 1/128 US gallon |
| Imperial fluid ounce | 28.4130625 mL | 1/160 imperial gallon |
| US dry ounce | ≈ 34.6 mL | A separate dry system, rare today |
So "8 ounces of water" is 236.6 mL in a US recipe but 227.3 mL in a British one. For exact formulations, watch the recipe's origin.
Cooking units are even less certain
| "1 cup" definition | Milliliters |
|---|---|
| US legal cup (nutrition labels) | 240 mL |
| US customary cup | ≈ 236.588 mL |
| Metric cup (Australia, Canada, etc.) | 250 mL |
| Japanese cup (カップ) | 200 mL |
The same "one cup" ranges from 200 to 250 mL — a 25% spread. For ratio-sensitive baking, weigh in grams rather than measuring by cup; how tightly you pack flour can shift one cup's weight by over 20%, which is why "I followed the recipe and it failed" happens. It is also why professional baking specs are written in grams.
Other common units
| Unit | Equivalent | Note |
|---|---|---|
| 1 cubic meter | 1000 L | 1 m³ = 1 kL |
| 1 cubic decimeter | 1 L | This is the definition of a liter |
| 1 cubic centimeter | 1 mL | Medical and dosage use |
| 1 barrel (oil) | 158.987294928 L | 42 US gallons; petroleum only |
| 1 bushel | ≈ 35.239 L (US, dry) | Agricultural; varies by country |
The fourth row deserves care: a "barrel" means different things per industry. An oil barrel is 42 US gallons (about 159 L), but beer barrels, paint pails, and chemical drums all differ. Crude is quoted per 42-gallon barrel — an industry convention, not a physical unit.
Conversion caveats
- Volume converts as a cube. Since 1 foot = 0.3048 m, then 1 cubic foot =
0.3048³ ≈ 0.0283 m³. Multiplying by 0.3048 once is wrong — this is the volume analog of the area squaring error (see the area tool for the square case). - Labeled capacity versus actual fill. A "1 L" container holds more to the brim; the nominal capacity is a specific fill line set by regulation.
- Temperature shifts liquid volume. Gasoline and oils traded by volume fix a temperature (commonly 15 ℃ or 20 ℃); thermal expansion is material in bulk trades, which is why mass settlement is more reliable.
- Volume is not capacity. A solid's "volume" and a container's "capacity" are different concepts; dosing, loading, and warehousing must distinguish them.
The tool covers cubic meter, liter, milliliter, cubic centimeter, cubic foot, cubic inch, US and imperial gallons, US and imperial fluid ounces, quart, pint, cup, tablespoon, teaspoon, and barrel — labeling US/imperial where it matters, all converted locally in the browser.
FAQ
Are US and UK gallons the same?
No. 1 US gallon ≈ 3.785 L, 1 UK gallon ≈ 4.546 L; the UK gallon is larger.
How many ml in a liter?
1 L = 1000 ml = 0.001 m³.