This converter turns US cups into imperial gallons instantly, using the exact factor 1 US cup = 0.05204213654 imperial 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.
The US legal cup used in recipes: 240 mL, or 236.6 mL by the customary definition. Exactly 4.54609 litres, about 20% larger than the US gallon.
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
US cups- The amount you are converting, measured in US cups
0.05204213654- The exact number of imperial gallons in one US cup
imperial gallons- The converted result
How it works, step by step
- Enter the number of US cups you want to convert.
- The value is multiplied by 0.05204213654, the exact conversion factor.
- The result is displayed in imperial gallons, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 US cups
Multiply 5 by 0.052042137. That gives 0.260211 imperial gallons. A quick sanity check: one US cup is smaller than one imperial gallon, so the number should get smaller — and it does.
Converting 72 US cups
72 × 0.052042137 = 3.747 imperial gallons. Working backwards, 3.747 ÷ 0.052042137 returns 72 US cups, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many imperial gallons are in one US cup?
Exactly 0.05204213654. 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 US cups to imperial gallons?
Imperial Gallons = US cups × 0.05204213654. To reverse it, divide instead: US cups = imperial gallons ÷ 0.05204213654, which is the same as multiplying by 19.21519881.
Is the US cup bigger than the imperial gallon?
No. One US cup is only 0.0520421 of a imperial gallon, so the imperial gallon is the larger unit.
Why does my answer differ slightly from other cups to imperial-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 US cup?
The US legal cup used in recipes: 240 mL, or 236.6 mL by the customary definition.
What is a imperial gallon?
Exactly 4.54609 litres, about 20% larger than the US gallon.
Us Cups to imperial gallons reference table
| Us Cups | Imperial Gallons |
|---|---|
| 0.5 cup | 0.026021 gal |
| 1 cup | 0.052042 gal |
| 2 cup | 0.104084 gal |
| 3 cup | 0.156126 gal |
| 5 cup | 0.260211 gal |
| 10 cup | 0.520421 gal |
| 15 cup | 0.780632 gal |
| 20 cup | 1.0408 gal |
| 25 cup | 1.3011 gal |
| 50 cup | 2.6021 gal |
| 75 cup | 3.9032 gal |
| 100 cup | 5.2042 gal |
| 250 cup | 13.0105 gal |
| 500 cup | 26.0211 gal |
| 1000 cup | 52.0421 gal |
Exact factor: 1 US cup = 0.05204213654 imperial gallons. Values rounded for display.