What is litre?
The litre is a metric unit of volume equal to one cubic decimetre. It is widely used for measuring liquid quantities in cooking, beverages, fuel, and laboratory work across metric countries.
Real-world uses
Litres are the global standard for beverage volumes, fuel tank capacities, engine displacement, and liquid medications. Water intake recommendations are given in litres (about 2 L/day), and swimming pools are measured in thousands of litres.
History
The litre was originally defined in 1795 as one cubic decimetre. In 1901 it was redefined based on the mass of water, creating a tiny discrepancy with the cubic decimetre. In 1964, the original definition (1 L = 1 dm³ exactly) was restored.
Common mistakes
Confusing litres with liters (both are correct—"litre" is the international spelling, "liter" is American). Also, assuming 1 litre of any liquid weighs 1 kg; this is only true for water at 4°C.
What is US gallon?
A US gallon is a volume unit equal to 128 US fluid ounces, or approximately 3.785 litres. It is the standard unit for fuel, milk, and other liquid products in the United States.
Real-world uses
US gallons are used for fuel pricing and vehicle fuel economy (miles per gallon) in the United States. Milk, water, and paint are commonly sold in gallon containers. Pool volumes and water heater capacities are specified in gallons.
History
The US gallon is based on the English wine gallon of 231 cubic inches, which was defined by Queen Anne in 1707. When Britain adopted the Imperial gallon in 1824 (based on water weight), the US retained the older wine gallon standard.
Common mistakes
Confusing US gallons with Imperial gallons: a US gallon is about 3.785 litres while an Imperial gallon is about 4.546 litres—roughly 20% larger. This causes major confusion when comparing fuel economy between US and UK figures.
When is this conversion used?
Converting between litre and US gallon is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Fuel economy, beverage volumes, and liquid measurements frequently require converting between litres and US gallons, especially for automotive and cooking contexts across different markets.
Worked examples
1 litre = 0.26417205 US gallon
1 US gallon = 3.78541178 litre
How to convert litre to US gallon
To convert litre to US gallon, multiply the value by 0.26417205.
To convert US gallon back to litre, multiply by 3.78541178.
Measurement standards
The cubic metre is the SI derived unit of volume. The litre, equal to exactly one cubic decimetre (0.001 m³), is accepted by the BIPM for use alongside SI units. Both the lowercase "l" and uppercase "L" are approved symbols for the litre.
Did you know?
An Olympic swimming pool holds 2,500 cubic metres of water — about 2.5 million litres. The Amazon River discharges roughly 209,000 cubic metres per second, enough to fill 84 Olympic pools every single second.
Quick reference: litre to US gallon
| litre | US gallon |
|---|---|
| 0.1 | 0.02641721 |
| 0.5 | 0.13208603 |
| 1 | 0.26417205 |
| 2 | 0.5283441 |
| 5 | 1.32086026 |
| 10 | 2.64172052 |
| 25 | 6.60430131 |
| 50 | 13.20860262 |
| 100 | 26.41720524 |
| 250 | 66.04301309 |
| 500 | 132.08602618 |
| 1,000 | 264.17205236 |
Common values
| litre | US gallon | |
|---|---|---|
| A teaspoon | 0.005 litre | 0.00132086 US gallon |
| A cup of coffee | 0.25 litre | 0.06604301 US gallon |
| A water bottle | 0.5 litre | 0.13208603 US gallon |
| A bathtub | 300 litre | 79.25161571 US gallon |
| A swimming pool (Olympic) | 2,500,000 litre | 660,430.13089537 US gallon |