This converter turns imperial gallons into US fluid ounces instantly, using the exact factor 1 imperial gallon = 153.7215905 US fluid ounces. 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. One eighth of a US cup, roughly 29.57 millilitres.
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
153.7215905- The exact number of US fluid ounces in one imperial gallon
US fluid ounces- The converted result
How it works, step by step
- Enter the number of imperial gallons you want to convert.
- The value is multiplied by 153.7215905, the exact conversion factor.
- The result is displayed in US fluid ounces, 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 153.72159. That gives 768.608 US fluid ounces. A quick sanity check: one imperial gallon is larger than one US fluid ounce, so the number should get bigger — and it does.
Converting 72 imperial gallons
72 × 153.72159 = 11,067.95 US fluid ounces. Working backwards, 11,067.95 ÷ 153.72159 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 fluid ounces are in one imperial gallon?
Exactly 153.7215905. 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 fluid ounces?
Us Fluid Ounces = imperial gallons × 153.7215905. To reverse it, divide instead: imperial gallons = US fluid ounces ÷ 153.7215905, which is the same as multiplying by 0.006505267067.
Is the imperial gallon bigger than the US fluid ounce?
Yes. One imperial gallon equals 153.722 US fluid ounces, so it is the larger unit.
Why does my answer differ slightly from other imperial-gallons to us-fluid-ounces 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 fluid ounce?
One eighth of a US cup, roughly 29.57 millilitres.
Imperial Gallons to US fluid ounces reference table
| Imperial Gallons | Us Fluid Ounces |
|---|---|
| 0.5 gal | 76.8608 fl oz |
| 1 gal | 153.7216 fl oz |
| 2 gal | 307.4432 fl oz |
| 3 gal | 461.1648 fl oz |
| 5 gal | 768.608 fl oz |
| 10 gal | 1,537.22 fl oz |
| 15 gal | 2,305.82 fl oz |
| 20 gal | 3,074.43 fl oz |
| 25 gal | 3,843.04 fl oz |
| 50 gal | 7,686.08 fl oz |
| 75 gal | 11,529.12 fl oz |
| 100 gal | 15,372.16 fl oz |
| 250 gal | 38,430.4 fl oz |
| 500 gal | 76,860.8 fl oz |
| 1000 gal | 153,721.59 fl oz |
Exact factor: 1 imperial gallon = 153.7215905 US fluid ounces. Values rounded for display.