5 L/min to GPM: Quick Flow Conversion Guide
- Imperial gallons per minute
- GPM
- Result
- Flow rate
- 5 L/min
- You entered
This guide converts a flow rate of 5 liters per minute (L/min) into gallons per minute (GPM) using both US and imperial gallons, and explains the simple math so you can convert any value. It’s for engineers, plumbers, hobbyists, and anyone working with pumps, pipes, or flow meters who needs a fast, accurate conversion.
Formula
The conversion uses two fixed factors, one for US gallons and one for imperial (UK) gallons:
US GPM = L/min × 0.264172
Imperial GPM = L/min × 0.219969
Where:
- L/min = flow rate in liters per minute (the value you input)
- US GPM = flow rate in US gallons per minute (1 US gal = 3.785411784 L)
- Imperial GPM = flow rate in imperial gallons per minute (1 imperial gal = 4.54609 L)
Worked Example
Using the default input of 5 L/min:
US GPM: 5 × 0.264172 = 1.32086 → rounded to 3 decimals = 1.321 GPM
Imperial GPM: 5 × 0.219969 = 1.099845 → rounded to 3 decimals = 1.100 GPM
So 5 liters per minute equals about 1.321 US gallons per minute, or 1.100 imperial gallons per minute.
Why the Difference Matters
The US gallon and the imperial gallon are not the same size. A US gallon is 3.785 liters, while an imperial gallon is 4.546 liters – about 20% larger. If you’re using a pump or flow meter from the UK or Australia, the readings are likely in imperial gallons. Mixing them up can lead to a 20% error in flow calculations, which is significant in dosing, cooling, or fuel systems.
When to Use This Conversion
Use this conversion whenever you need to compare flow rates between metric and US customary systems. Common scenarios include sizing a pump for a pool, reading a European flow meter for a US system, or checking the output of a water filter. Always confirm which gallon your equipment uses – the label usually says “US” or “UK/imperial.”
Common Mistakes
The most frequent error is using the wrong gallon factor. Another is rounding too early – for example, using 0.26 instead of 0.264172 changes the result by about 1.5%. Also, remember that “gpm” in most American industrial contexts means US gallons, but in countries like Canada and the UK, it may mean imperial. When in doubt, ask or check the equipment manual.
How to Choose
When converting flow rates, the only real choice is which gallon standard to use. If you’re in the US or working with US-made equipment, use US gallons. If you’re in the UK, Australia, or using equipment from those regions, use imperial gallons. For international projects, state both values to avoid confusion. The calculator above gives both, so you don’t have to remember the factors.
Frequently Asked Questions
How many US gallons per minute is 5 L/min?
5 L/min is approximately 1.321 US GPM (using the exact factor 0.264172).
How many imperial gallons per minute is 5 L/min?
5 L/min is approximately 1.100 imperial GPM (using the exact factor 0.219969).
Why are there two different gallons?
Historically, the US and UK defined their gallons differently. The US gallon is based on a wine gallon of 231 cubic inches, while the imperial gallon is based on 10 pounds of water. The imperial gallon is about 20% larger.
Can I use this conversion for any flow rate?
Yes, the conversion factors are constant. Just multiply any L/min value by 0.264172 for US GPM or by 0.219969 for imperial GPM.
What if my flow meter shows GPM but I need L/min?
Simply divide the GPM by the same factor. For US GPM to L/min: GPM ÷ 0.264172. For imperial GPM to L/min: GPM ÷ 0.219969.
Is there a difference between “gallon” and “gal” in formulas?
No, they are the same unit. But always check the context – “gal” in a US manual means US gallons, while in a UK manual it means imperial gallons.
Final Thoughts
Converting 5 L/min to GPM is straightforward once you know which gallon you’re using. The difference between US and imperial gallons is large enough to cause real problems in practical applications, so always double-check. With the formula and calculator above, you can convert any flow rate accurately in seconds.
Related
Formula used
in rate | Flow rate | L/min | 5 | 0 out us_gpm | US gallons per minute | GPM | rate * 0.264172 | 3 out imp_gpm | Imperial gallons per minute | GPM | rate * 0.219969 | 3
Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work
Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.