This page converts imperial gallons per minute into US gallons per minute using the factor 1.200949925, and shows the reverse figure alongside it. Both units measure volumetric flow, which is why one number does the whole job.
The US standard for pumps, irrigation and fixtures. The British pump unit, about 20% more volume per minute than the US gallon version.
Standard versus actual volume. Gas flow in CFM depends on pressure and temperature, which is why compressor ratings say SCFM and specify the reference conditions. Converting the number is exact; comparing two ratings measured at different conditions is not. Two tables follow: rounded steps for quick lookup, and a set of real reference quantities converted into US gallons per minute, which is usually more useful than the bare number.
The formula
imperial gallons per minute- The amount you are converting, in imperial gallons per minute
1.20094992544- The exact number of US gallons per minute in one imperial gallon per minute
US gallons per minute- The converted result
How it works, step by step
- Enter the value in imperial gallons per minute.
- It is multiplied by 1.20094992544, the exact factor between the two units.
- The answer is shown in US gallons per minute, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
The Thames at London: 8.58e+05 gpm in US gallons per minute
Take the thames at london, roughly 8.58e+05 gpm. The conversion is a single multiplication — 8.58e+05 × 1.20095 — giving 1.03042e+06 GPM. Because the relationship is proportional, doubling the input doubles the answer to 2.06083e+06 GPM.
A garden hose: 3.96 gpm in US gallons per minute
At 3.96 gpm (a garden hose), the same quantity in US gallons per minute is 3.96 × 1.20095 = 4.75576 GPM. One imperial gallon per minute is 1.20095 US gallons per minute, so the numbers grow as expected.
How to read your score
Frequently asked questions
How many US gallons per minute are in one imperial gallon per minute?
Exactly 1.20094992544. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert imperial gallons per minute to US gallons per minute?
US gallons per minute = imperial gallons per minute × 1.20094992544. Reversed, imperial gallons per minute = US gallons per minute ÷ 1.20094992544, which is the same as multiplying by 0.832674184674.
Which is the bigger unit, the imperial gallon per minute or the US gallon per minute?
The imperial gallon per minute. One imperial gallon per minute equals 1.20095 US gallons per minute.
What does this quantity actually measure?
Both units measure volumetric flow. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a imperial gallon per minute?
The British pump unit, about 20% more volume per minute than the US gallon version.
What is a US gallon per minute?
The US standard for pumps, irrigation and fixtures.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do gpm to GPM in my head?
Plenty of people do this in their head: multiply by 1.2 instead of using the exact factor 1.200949925. At 100 that shortcut gives 120 US gallons per minute, off by 0.09499 US gallons per minute or about 0.08%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Imperial Gallons Per Minute to US gallons per minute reference tables
| Imperial Gallons Per Minute | Us Gallons Per Minute |
|---|---|
| 0.5 gpm | 0.600475 GPM |
| 1 gpm | 1.20095 GPM |
| 2 gpm | 2.4019 GPM |
| 3 gpm | 3.60285 GPM |
| 5 gpm | 6.00475 GPM |
| 10 gpm | 12.0095 GPM |
| 20 gpm | 24.019 GPM |
| 25 gpm | 30.0237 GPM |
| 50 gpm | 60.0475 GPM |
| 75 gpm | 90.0712 GPM |
| 100 gpm | 120.095 GPM |
| 250 gpm | 300.237 GPM |
| 500 gpm | 600.475 GPM |
| 1000 gpm | 1200.95 GPM |
| 5000 gpm | 6004.75 GPM |
Exact factor: 1 imperial gallon per minute = 1.20094992544 US gallons per minute.
| Quantity | gpm | GPM |
|---|---|---|
| A dripping tap | 0.00132 gpm | 0.001585 GPM |
| A bathroom tap | 1.32 gpm | 1.585 GPM |
| A shower head | 2.112 gpm | 2.536 GPM |
| A garden hose | 3.959 gpm | 4.755 GPM |
| A fire hydrant | 791.9 gpm | 951 GPM |
| The Thames at London | 8.579e+05 gpm | 1.03e+06 GPM |
Published reference values, converted with the same factor this page uses.