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Volume Converter (US and Imperial)
Convert liquid and general volumes between metric, US customary and imperial units. US and imperial gallons, pints and ounces are listed separately so you never have to guess which is meant.
US gallon versus imperial gallon
The US liquid gallon is exactly 3.785411784 litres (231 cubic inches). The imperial gallon, used historically in the UK and some Commonwealth countries, is exactly 4.54609 litres. The imperial gallon is therefore about 20% larger: 1 imperial gallon equals roughly 1.20095 US gallons.
The sub-units split differently too. The US gallon holds 4 quarts, 8 pints, 16 cups or 128 fluid ounces. The imperial gallon holds 4 quarts, 8 pints and 160 fluid ounces, because an imperial pint is 20 fluid ounces rather than 16.
| Unit | US (mL) | Imperial (mL) |
|---|---|---|
| Fluid ounce | 29.5735 | 28.4131 |
| Pint | 473.176 | 568.261 |
| Quart | 946.353 | 1,136.52 |
The litre and cubic units
The litre is defined as one cubic decimetre, so 1 L = 1,000 cm³ = 0.001 m³ exactly, and 1 mL is one cubic centimetre. A cubic metre therefore holds 1,000 litres. For imperial cubic units, one cubic foot is 28.316846592 L and one cubic inch is 0.016387064 L, both exact because the inch is exactly 25.4 mm.
Where volume conversions go wrong
- Not saying which gallon. A recipe or fuel figure labelled only "gallon" may be either. Check the country of origin of the source.
- Fluid ounces versus weight ounces. A fluid ounce measures volume. Only water-like liquids weigh close to an ounce per fluid ounce, and that is not the same unit.
- Spoon sizes. The US tablespoon here is 14.787 mL. Some countries use a 15 mL metric tablespoon, and Australia uses 20 mL. Teaspoons are similar: 4.929 mL here versus 5 mL in metric recipes.
- Dry measures. US dry pints, quarts and bushels are a separate set of units and are not included.
Mental shortcuts
A litre is a little more than a US quart (1.057 quarts). A US gallon is about 3.8 litres, and an imperial gallon is about 4.5 litres. To compare fuel prices or tank sizes across the two systems, multiply imperial gallons by 1.2 to get US gallons. A cubic metre is about 35.3 cubic feet. When precision matters, as in medicine, chemistry or engineering, use the exact conversion from the calculator rather than these approximations.
Everyday uses include recipes written for another country, car and boiler capacities, aquarium and water tank sizes, and shipping or storage volumes. For ingredients measured by weight, the cooking converter handles the volume-to-mass step.
Note that fuel economy figures such as miles per gallon depend on which gallon was used. A car rated at 40 miles per imperial gallon covers about 33 miles per US gallon, so always compare like with like.
Worked example
A US fuel tank holds 10 US gallons. How many litres is that?
Inputs
| Value | 10 |
|---|---|
| From | US gallons (US gal) |
| To | Litres (L) |
Result
10 US gal = 37.854118 L
| Millilitres (mL) | 37,854.1178 |
|---|---|
| Cubic metres (m³) | 0.03785412 |
| US teaspoons (US tsp) | 7,680 |
| US tablespoons (US tbsp) | 2,560 |
| US fluid ounces (US fl oz) | 1,280 |
| US cups (US cup) | 160 |
| US pints (US pt) | 80 |
| US quarts (US qt) | 40 |
| Imperial fluid ounces (imp fl oz) | 1,332.2787 |
| Imperial pints (imp pt) | 66.613935 |
| Imperial quarts (imp qt) | 33.306967 |
| Imperial gallons (imp gal) | 8.326742 |
| Cubic feet (ft³) | 1.336806 |
| Cubic inches (in³) | 2,310 |
- Factors are exact definitions where one exists; results are shown to about six significant digits.
Accuracy note: Factors use the standard definitions stated on this page. Results are rounded for display; for engineering or legal work use the full-precision factors.
Frequently asked questions
How many litres are in a US gallon?
A US liquid gallon is exactly 3.785411784 litres, which is defined as 231 cubic inches. Multiply gallons by that figure to get litres.
How many litres are in an imperial gallon?
An imperial gallon is exactly 4.54609 litres, about 20% more than a US gallon.
How many US cups are in a litre?
A litre holds about 4.2268 US cups, because one US cup is 236.5882365 millilitres.
Why do US and imperial pints differ?
The US pint is one eighth of a US gallon (16 US fluid ounces), while the imperial pint is one eighth of an imperial gallon (20 imperial fluid ounces). The underlying gallons have different sizes.
Does this converter cover dry volumes?
No. It covers liquid and general volume units. US dry measures such as the dry pint and bushel are different units and are left out to avoid confusion.
Related calculators
More conversion references
For volume conversion tables beyond this tool, see PakMath volume conversion tables. PakMath is a sister project of Adzita.