Convert Imperial gallons to US gallons
1 imperial gallon is 1.2 gal. One imperial gallon is exactly 1.2009499255 US gallons.
One imperial gallon is 1.2009499 US gallons. To convert imperial gallons to US gallons, multiply by 1.2009499; to go the other way, divide by 1.2009499 or multiply by 0.83267418. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST Handbook 130.
Factor checked against the defining standard · How we check
- Imperial gallons × 1.2009499
1 * 1.20094991.201 gal
1 imperial gallon in every volume unit
| Unit | Value | Exact factor |
|---|---|---|
| US teaspoons | 922.3295428 tsp | × 922.329542788 |
| US tablespoons | 307.4431809 tbsp | × 307.443180929 |
| US fluid ounces | 153.7215905 fl oz | × 153.721590465 |
| US cups | 19.21519881 cup | × 19.2151988081 |
| US pints | 9.607599404 pt | × 9.60759940404 |
| US quarts | 4.803799702 qt | × 4.80379970202 |
| US gallons | 1.200949926 gal | × 1.2009499255 |
| milliliters | 4,546.09 ml | × 4,546.09 |
| liters | 4.54609 L | × 4.54609 |
| imperial gallons (as entered) | 1 gal (UK) | — |
| imperial quarts | 4 qt (UK) | × 4 |
| imperial pints | 8 pt (UK) | × 8 |
| imperial fluid ounces | 160 fl oz (UK) | × 160 |
| imperial gills | 32 gi (UK) | × 32 |
| cubic millimetres | 4,546,090 mm³ | × 4,546,090 |
| cubic centimetres | 4,546.09 cm³ | × 4,546.09 |
| cubic inches | 277.4194328 in³ | × 277.419432792 |
| cubic feet | 0.1605436532 ft³ | × 0.160543653236 |
| cubic yards | 0.005946061231 yd³ | × 0.00594606123096 |
| cubic metres | 0.00454609 m³ | × 0.00454609 |
Factors are entered by hand from NIST Handbook 130 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert imperial gallons to US gallons? The converter and the working
- 1.Take the measurement in imperial gallons.
- 2.Multiply by 1.2009499 — that is how many US gallons fit in one imperial gallon.
- 3.To go back the other way, divide by 1.2009499, or multiply by 0.83267418.
Worked example: 25 imperial gallons to US gallons
- Formula
- gal (UK) × 1.2009499 = gal
- Arithmetic
- 25 × 1.2009499 = 30.02 gal
- Answer
- 25 gal (UK) = 30.02 gal
The factor is rounded for display; the figure above is computed from the full value.
Imperial gallons to US gallons conversion table
| Imperial gallons | US gallons |
|---|---|
| 1 gal (UK) | 1.2 gal |
| 2 gal (UK) | 2.4 gal |
| 3 gal (UK) | 3.6 gal |
| 4 gal (UK) | 4.8 gal |
| 5 gal (UK) | 6 gal |
| 6 gal (UK) | 7.21 gal |
| 7 gal (UK) | 8.41 gal |
| 8 gal (UK) | 9.61 gal |
| 9 gal (UK) | 10.81 gal |
| 10 gal (UK) | 12.01 gal |
| 12 gal (UK) | 14.41 gal |
| 15 gal (UK) | 18.01 gal |
| 20 gal (UK) | 24.02 gal |
| 25 gal (UK) | 30.02 gal |
| 50 gal (UK) | 60.05 gal |
| 100 gal (UK) | 120.09 gal |
| 200 gal (UK) | 240.19 gal |
| 300 gal (UK) | 360.28 gal |
| 500 gal (UK) | 600.47 gal |
| 1000 gal (UK) | 1,200.95 gal |
| 2000 gal (UK) | 2,401.9 gal |
| 5000 gal (UK) | 6,004.75 gal |
| 10000 gal (UK) | 12,009.5 gal |
The two gallons differ by 20%, which is why mpg figures do not compare
An imperial gallon is 4.54609 liters exactly; a US gallon is 3.785411784. A British car doing 40 mpg is doing about 33 US mpg on the same fuel, and a US car rated 30 mpg would be advertised as 36 in the UK. Neither country converts the figure when quoting the other’s, which is how the same engine ends up with two economy numbers that look like a mistake.
NIST Handbook 44, Appendix C — general tables of units of measurement
What is an imperial gallon?
Exactly 4.54609 liters since 1985, and the reason UK and US fuel economy figures cannot be compared: it is 20% larger than the US gallon, so 40 mpg in Britain is about 33 mpg in America on the same car.
What is a US gallon?
Exactly 231 cubic inches. The imperial gallon is 4.546 liters, so US and UK fuel economy figures are not comparable.
How many US gallons are in an imperial gallon?
One imperial gallon is 1.2009499 US gallons. Going the other way, one US gallon is 0.83267418 imperial gallons. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every volume unit here
The whole group — 20 units with their symbols and the size of each one in liters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to an imperial gallon.
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Questions people actually ask
- How many US gallons are in an imperial gallon?
- 1.2009499. Exactly 231 cubic inches. The imperial gallon is 4.546 liters, so US and UK fuel economy figures are not comparable.
- How do I convert US gallons back to imperial gallons?
- Divide by 1.2009499, or multiply by 0.83267418 — they are the same operation.
Other volume conversions
US gallons to imperial gallons — the same conversion the other way.