Imperial Gallon (gal (imp))
The imperial gallon is defined as exactly 4.54609 litres, about 20 % larger than the US gallon.
Symbol: gal (imp) (ASCII: imp gal)
Quantity: volume (capacity)
SI relation: 1 gal (imp) = 0.00454609 m³ (exact)
Derivation: 1 imp gal = 4.54609 L = 0.00454609 m³ (exact, by definition)
Exact: yes, by definition
History
Defined in 1824 as the volume of 10 lb of water; the UK Weights and Measures Act 1985 fixed it at exactly 4.54609 L.
Typical uses
- Fuel economy in the UK (miles per gallon)
- Older UK and Commonwealth tank and pump ratings
- Brewing and agriculture in the UK
Convert imperial gallons to other units
| Conversion | 1 gal (imp) equals | Reverse |
|---|---|---|
| imperial gallon to cubic meter | 0.00454609 m³ | cubic meter to imperial gallon |
| imperial gallon to liter | 4.54609 L | liter to imperial gallon |
| imperial gallon to milliliter | 4546.09 mL | milliliter to imperial gallon |
| imperial gallon to cubic foot | 0.1605436532 ft³ | cubic foot to imperial gallon |
| imperial gallon to US gallon | 1.200949926 gal (US) | US gallon to imperial gallon |
| imperial gallon to cubic centimeter | 4546.09 cm³ | cubic centimeter to imperial gallon |
| imperial gallon to cubic inch | 277.4194328 in³ | cubic inch to imperial gallon |
Open the Volume Converter to convert any value between all units.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "gallon [Canadian and U.K. (Imperial)]".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Imperial Gallon (gal (imp)). Retrieved October 17, 2026, from https://scientificconverters.com/units/imperial-gallon/
IEEE
Scientific Converters, "Imperial Gallon (gal (imp))," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/units/imperial-gallon/