About this calculator
US and UK gallons are different sizes, so both are listed.
How to use it
- Enter the value.
- Choose the unit it is in and the unit you want.
- Read the result, or see every unit in the table.
The formula
Result = value × (litres in the “from” unit) ÷ (litres in the “to” unit)
- 1 US gallon
- 3.785 L
- 1 UK gallon
- 4.546 L
- 1 m³
- 1,000 L
- 1 US cup
- 236.6 ml
Worked example
Tanks and recipes
- 1 US gallon = 3.785 litres.
- A 1,000-litre water tank holds 1 cubic metre, or 35.3 cubic feet.
- 1 US cup = 236.6 ml, about 16 tablespoons.
What the result means
The factors are exact international definitions, so results are as accurate as the digits shown.
Assumptions
- US customary cups and spoons.
Limitations
- Indian kitchen cups and spoons vary; check your measuring set.
Frequently asked questions
How many litres in a gallon?
3.785 L in a US gallon and 4.546 L in a UK gallon.
How many litres in 1 cubic metre?
1,000.
How many ml in a cup?
About 237 ml in a US cup; metric cups are 250 ml.
Last reviewed on 3 October 2026. Found a mistake? Tell us.