Volume Converter
Not All Gallons Are the Same Gallon
The US gallon is 3.785411784 litres. The imperial gallon is 4.54609 litres. They share a name and differ by 20% — which is why a car rated at 40 miles per gallon in Britain is not the same car rated at 40 mpg in America, and why a recipe calling for a pint means 473 ml on one side of the Atlantic and 568 ml on the other. This converter keeps the two systems strictly separate, so the gallon you pick is the gallon you get.
The Formula
Twelve units, one pivot. Each is stored as its capacity in litres:
(Factors are relative to 1 liter)
Negative input is refused — a container cannot hold less than nothing. Everything else routes through litres: 5 US gallons to litres is 5 × 3.785411784 ÷ 1.0 = 18.92705892 L.
The Factors
| Unit | Code | Litres per unit |
|---|---|---|
| Milliliters | ml | 0.001 |
| Cubic Centimeters | cm3 | 0.001 |
| Liters | l | 1 |
| Cubic Meters | m3 | 1000 |
| US Fluid Ounces | us_floz | 0.0295735295625 |
| US Cups | us_cup | 0.2365882365 |
| US Pints | us_pint | 0.473176473 |
| US Quarts | us_qt | 0.946352946 |
| US Gallons | us_gal | 3.785411784 |
| Imperial Gallons | imp_gal | 4.54609 |
| Cubic Inches | in3 | 0.016387064 |
| Cubic Feet | ft3 | 28.316846592 |
A millilitre and a cubic centimetre are the same volume by definition — both are 0.001 L. Medicine and cooking say ml; engines and engineering say cc.
Complete Cross-Reference
| 1 of… | Liters | Milliliters | US Gallons | Imp Gallons | Cubic Feet |
|---|---|---|---|---|---|
| Milliliter | 0.001 | 1 | 0.00026417 | 0.00021997 | 0.00003531 |
| Liter | 1 | 1000 | 0.26417205 | 0.21996925 | 0.03531467 |
| Cubic Meter | 1000 | 1000000 | 264.17205236 | 219.9692483 | 35.31466672 |
| US Fluid Ounce | 0.02957353 | 29.57352956 | 0.0078125 | 0.00650527 | 0.00104438 |
| US Cup | 0.23658824 | 236.5882365 | 0.0625 | 0.05204214 | 0.00835503 |
| US Pint | 0.47317647 | 473.176473 | 0.125 | 0.10408427 | 0.01671007 |
| US Quart | 0.94635295 | 946.352946 | 0.25 | 0.20816855 | 0.03342014 |
| US Gallon | 3.78541178 | 3785.411784 | 1 | 0.83267418 | 0.13368056 |
| Imperial Gallon | 4.54609 | 4546.09 | 1.20094993 | 1 | 0.16054365 |
| Cubic Inch | 0.01638706 | 16.387064 | 0.004329 | 0.00360465 | 0.0005787 |
| Cubic Foot | 28.31684659 | 28316.846592 | 7.48051948 | 6.22883546 | 1 |
Kitchen Measures in Millilitres
| Measure | Milliliters |
|---|---|
| 1 US fluid ounce | 29.57352956 |
| 1 US cup | 236.5882365 |
| 1 US pint | 473.176473 |
| 1 US quart | 946.352946 |
Fuel and Fluid Quantities
| US Gallons | Liters |
|---|---|
| 1 | 3.78541178 |
| 2 | 7.57082357 |
| 5 | 18.92705892 |
| 10 | 37.85411784 |
| 15 | 56.78117676 |
| 20 | 75.70823568 |
Where It Matters
- Cooking from foreign recipes — American recipes measure liquid by volume in cups; most of the rest of the world uses millilitres. A cup is 236.59 ml, not the 250 ml some conversions assume — a 5.7% difference.
- Fuel economy comparisons — converting mpg figures between markets requires knowing which gallon the original figure used. The imperial gallon is 1.20094993 US gallons, so a UK mpg number looks 20% better than the same car's US number.
- Aquariums, tanks and pools — capacity computed from dimensions comes out in cubic feet or cubic metres and has to be reported in gallons or litres.
- Engine displacement — a 350 cubic inch engine and a 5.7 litre engine are the same engine, described in two conventions.
How to Use This Calculator
- Enter the volume in the Value field — zero or positive.
- Choose the unit it's currently in from the first dropdown. If a source says just "gallons", check whether it's US or Imperial before selecting.
- Choose the unit you want from the second dropdown.
- Press Calculate. The result shows both factors used and the division performed.
Related Calculations
Converting mass rather than capacity? The Weight Converter handles kilograms, pounds and ounces. For tank and container capacity work with a barrels-and-bulk emphasis, see the Volume Unit Converter.