Convert US Gallons to Imperial Gallons
1 US gallon (gal (US)) equals 0.8326741846 imperial gallons (gal (imp)).
1 gal (US) = 0.8326741846 gal (imp)
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk US gallon to imperial gallon converter to paste a column from Excel.
How to Convert US Gallon to Imperial Gallon
- 1 gal (US) = 0.8326741846 gal (imp)
- 1 gal (imp) = 1.200949926 gal (US)
- Example: convert 15 gal (US) to gal (imp): 15 gal (US) = 15 × 0.8326741846 gal (imp) = 12.49011277 gal (imp)
Formula
gal (imp) = gal (US) × 0.832674184629
or gal (imp) = gal (US) ÷ 1.200949925505
Derivation from SI units:
- 1 US gal = 231 in³ = 231 × (0.0254 m)³ = 0.003785411784 m³
- 1 imp gal = 4.54609 L = 0.00454609 m³ (exact, by definition)
- 1 gal (US) = 0.003785411784 m³ ÷ 0.00454609 m³ per gal (imp) = 0.832674184629 gal (imp)
Both units are defined exactly, so the factor is exact. US Gallon definition: US gallon; Imperial Gallon definition: imperial gallon.
Worked examples
- 1 gal (US) is 0.8326741846 gal (imp).
1 gal (US) × 0.8326741846 = 0.8326741846 gal (imp) - A 15 gal (US) fuel tank holds 12.49011277 gal (imp).
15 gal (US) × 0.8326741846 = 12.49011277 gal (imp)
US Gallon to Imperial Gallon conversion table
| US Gallons (gal (US)) | Imperial Gallons (gal (imp)) |
|---|---|
| 0.25 gal (US) | 0.2081685462 gal (imp) |
| 0.5 gal (US) | 0.4163370923 gal (imp) |
| 1 gal (US) | 0.8326741846 gal (imp) |
| 2 gal (US) | 1.665348369 gal (imp) |
| 2.5 gal (US) | 2.081685462 gal (imp) |
| 5 gal (US) | 4.163370923 gal (imp) |
| 10 gal (US) | 8.326741846 gal (imp) |
| 15 gal (US) | 12.49011277 gal (imp) |
| 20 gal (US) | 16.65348369 gal (imp) |
| 25 gal (US) | 20.81685462 gal (imp) |
| 50 gal (US) | 41.63370923 gal (imp) |
| 55 gal (US) | 45.79708015 gal (imp) |
| 100 gal (US) | 83.26741846 gal (imp) |
| 275 gal (US) | 228.9854008 gal (imp) |
| 330 gal (US) | 274.7824809 gal (imp) |
| 500 gal (US) | 416.3370923 gal (imp) |
| 1000 gal (US) | 832.6741846 gal (imp) |
| 10000 gal (US) | 8326.741846 gal (imp) |
Where it's used
Comparing US and UK fuel economy or tank sizes requires converting between the two gallons.
US Gallon to other volume units
| Conversion | 1 gal (US) equals |
|---|---|
| US gallon to cubic meter | 0.003785411784 m³ |
| US gallon to liter | 3.785411784 L |
| US gallon to milliliter | 3785.411784 mL |
| US gallon to cubic centimeter | 3785.411784 cm³ |
| US gallon to cubic foot | 0.1336805556 ft³ |
| US gallon to cubic inch | 231 in³ |
| US gallon to imperial gallon | 0.8326741846 gal (imp) |
Frequently asked questions
How do I convert US mpg to UK mpg?
Multiply by about 1.201, the ratio of the imperial to the US gallon.
How many imperial gallons are in 1 US gallon?
1 gal (US) = 0.8326741846 gal (imp).
How do I convert US gallons to imperial gallons?
Multiply the value in gal (US) by 0.8326741846, or divide it by 1.200949926. For example, 15 gal (US) × 0.8326741846 = 12.49011277 gal (imp).
Is the gal (US) to gal (imp) conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
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 [U.S.] (gal)".
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement, National Institute of Standards and Technology , Appendix C.
- 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). Convert US Gallons to Imperial Gallons. Retrieved October 17, 2026, from https://scientificconverters.com/volume/us-gallons-to-imperial-gallons/
IEEE
Scientific Converters, "Convert US Gallons to Imperial Gallons," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/volume/us-gallons-to-imperial-gallons/