Imperial gallon (gal (Imp))
1 Imperial gallon = 4.54609 litres
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.
Notes: Imperial unit
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 Imperial gallon and litre 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.
How to convert Imperial gallon to litre
To convert Imperial gallon to litre, multiply the value by 4.54609.
Conversion formula (from base unit)
x * 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.
| Imperial gallons | litres |
|---|---|
| 0.1 | 0.454609 |
| 0.5 | 2.273045 |
| 1 | 4.54609 |
| 2 | 9.09218 |
| 5 | 22.73045 |
| 10 | 45.4609 |
| 25 | 113.65225 |
| 50 | 227.3045 |
| 100 | 454.609 |
| 250 | 1,136.5225 |
| 500 | 2,273.045 |
| 1,000 | 4,546.09 |
Common values
| Imperial gallons | litres | |
|---|---|---|
| A teaspoon | 0.00109985 Imperial gallons | 0.005 litres |
| A cup of coffee | 0.05499231 Imperial gallons | 0.25 litres |
| A water bottle | 0.10998462 Imperial gallons | 0.5 litres |
| A bathtub | 65.99077449 Imperial gallons | 300 litres |
| A swimming pool (Olympic) | 549,923.12074772 Imperial gallons | 2,500,000 litres |
Full Imperial gallon conversion table
| Unit | Value | Factor |
|---|---|---|
| litre | 1 gal (Imp) = 4.54609 L | × 4.54609 |
| millilitre | 1 gal (Imp) = 4,546.09 mL | × 4,546.09 |
| US gallon | 1 gal (Imp) = 1.20094993 gal (US) | × 1.20094993 |
| cubic metre | 1 gal (Imp) = 0.00454609 m³ | × 0.00454609 |
| US fluid ounce | 1 gal (Imp) = 153.72159046 fl oz (US) | × 153.72159046 |
| Imperial fluid ounce | 1 gal (Imp) = 160 fl oz (Imp) | × 160 |
| teaspoon (metric) | 1 gal (Imp) = 909.218 tsp | × 909.218 |
| tablespoon (metric) | 1 gal (Imp) = 303.07266667 Tbsp | × 303.07266667 |
| cubic centimetre | 1 gal (Imp) = 4,546.09 cm³ | × 4,546.09 |