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 Imperial gallon?
An Imperial gallon is a volume unit used in the United Kingdom equal to approximately 4.546 litres. It is larger than the US gallon and is commonly referenced for fuel efficiency (miles per gallon) in the UK.
Real-world uses
Imperial gallons are used in the United Kingdom, Canada (for some purposes), and several Caribbean countries. British fuel economy was historically quoted in miles per Imperial gallon. Older Commonwealth-era recipes and industrial specifications may reference Imperial gallons.
History
The Imperial gallon was established by the British Weights and Measures Act of 1824 as the volume occupied by 10 pounds of water at 62°F (≈ 17°C). It replaced several older gallon definitions including the wine gallon (retained by the US) and the ale gallon.
Common mistakes
Assuming the Imperial gallon equals the US gallon. The Imperial gallon is about 4.546 litres versus 3.785 litres for the US gallon. Converting mpg figures between the two systems without adjusting for gallon size gives misleading results.
When is this conversion used?
Converting between litre and Imperial 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 = 0.21996925 Imperial gallon
1 Imperial gallon = 4.54609 litre
How to convert litre to Imperial gallon
To convert litre to Imperial gallon, multiply the value by 0.21996925.
To convert Imperial gallon back to litre, multiply by 4.54609.
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 Imperial gallon
| litre | Imperial gallon |
|---|---|
| 0.1 | 0.02199692 |
| 0.5 | 0.10998462 |
| 1 | 0.21996925 |
| 2 | 0.4399385 |
| 5 | 1.09984624 |
| 10 | 2.19969248 |
| 25 | 5.49923121 |
| 50 | 10.99846241 |
| 100 | 21.99692483 |
| 250 | 54.99231207 |
| 500 | 109.98462415 |
| 1,000 | 219.9692483 |
Common values
| litre | Imperial gallon | |
|---|---|---|
| A teaspoon | 0.005 litre | 0.00109985 Imperial gallon |
| A cup of coffee | 0.25 litre | 0.05499231 Imperial gallon |
| A water bottle | 0.5 litre | 0.10998462 Imperial gallon |
| A bathtub | 300 litre | 65.99077449 Imperial gallon |
| A swimming pool (Olympic) | 2,500,000 litre | 549,923.12074772 Imperial gallon |