This converter turns imperial gallons into US gallons instantly, using the exact factor 1 imperial gallon = 1.200949926 US gallons. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
Exactly 4.54609 litres, about 20% larger than the US gallon. Exactly 231 cubic inches — the US liquid gallon used for fuel and milk.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
imperial gallons- The amount you are converting, measured in imperial gallons
1.200949926- The exact number of US gallons in one imperial gallon
US gallons- The converted result
How it works, step by step
- Enter the number of imperial gallons you want to convert.
- The value is multiplied by 1.200949926, the exact conversion factor.
- The result is displayed in US gallons, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 imperial gallons
Multiply 5 by 1.2009499. That gives 6.0047 US gallons. A quick sanity check: one imperial gallon is larger than one US gallon, so the number should get bigger — and it does.
Converting 72 imperial gallons
72 × 1.2009499 = 86.4684 US gallons. Working backwards, 86.4684 ÷ 1.2009499 returns 72 imperial gallons, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many US gallons are in one imperial gallon?
Exactly 1.200949926. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert imperial gallons to US gallons?
Us Gallons = imperial gallons × 1.200949926. To reverse it, divide instead: imperial gallons = US gallons ÷ 1.200949926, which is the same as multiplying by 0.8326741846.
Is the imperial gallon bigger than the US gallon?
Yes. One imperial gallon equals 1.20095 US gallons, so it is the larger unit.
Why does my answer differ slightly from other imperial-gallons to us-gallons converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a imperial gallon?
Exactly 4.54609 litres, about 20% larger than the US gallon.
What is a US gallon?
Exactly 231 cubic inches — the US liquid gallon used for fuel and milk.
Imperial Gallons to US gallons reference table
| Imperial Gallons | Us Gallons |
|---|---|
| 0.5 gal | 0.600475 gal |
| 1 gal | 1.2009 gal |
| 2 gal | 2.4019 gal |
| 3 gal | 3.6028 gal |
| 5 gal | 6.0047 gal |
| 10 gal | 12.0095 gal |
| 15 gal | 18.0142 gal |
| 20 gal | 24.019 gal |
| 25 gal | 30.0237 gal |
| 50 gal | 60.0475 gal |
| 75 gal | 90.0712 gal |
| 100 gal | 120.095 gal |
| 250 gal | 300.2375 gal |
| 500 gal | 600.475 gal |
| 1000 gal | 1,200.95 gal |
Exact factor: 1 imperial gallon = 1.200949926 US gallons. Values rounded for display.