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The flow rate in US gallons per minute.
A US gallon is 3.785 litres; an imperial gallon is 4.546 litres, about 20% larger. UK flow figures quoted in gallons may mean either, so confirm which.
Flow rate
37.85 L/min
1 US gallon = 3.785411784 L exactly, so GPM × 3.7854 gives L/min. A US gallon and an imperial gallon differ by about 20% — confirm which the source figure uses.
- Conversion factor applied
- 3.79 L/min per GPM
They open the calculator with your figures already in it
GPM to Litres per Minute Calculator: 37.85 L/min — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- 1 US liquid gallon = 231 cubic inches = 3.785411784 L exactly
- 1 imperial gallon = 4.54609 L, roughly 20% larger than a US gallon
Inputs used
- Flow rate (GPM)
- 10
Intermediate steps
- Conversion factor applied
- 3.79 L/min per GPM
Confidence note: 1 US gallon = 3.785411784 L exactly, so GPM × 3.7854 gives L/min. A US gallon and an imperial gallon differ by about 20% — confirm which the source figure uses.
What this calculation does not cover
- The factor is the US liquid gallon. An imperial gallon is about a fifth larger, and nothing here can tell which one your source figure used - a UK gallons-per-minute figure entered as if it were US gallons converts low, with no warning on the page.
- The time base is assumed, not checked. This converts gallons per MINUTE only: a gallons-per-hour figure typed in unchanged comes out 60 times too high, and a gallons-per-day figure 1,440 times too high. The same trap runs the other way for European data quoted in litres per second.
- This is a unit conversion, not a hydraulic calculation. It carries no pipe bore, velocity limit, friction loss, static head or pump curve, so the converted number says nothing about whether that flow can actually be delivered through a given pipe or by a given pump.
- A rated flow belongs to the conditions it was measured under - a pump duty point, an inlet pressure, a nozzle size. The conversion moves the number and leaves those conditions behind, so two flows in matching units are still only comparable if their test conditions match. For gas and compressed air this bites harder: those flows are quoted at a stated reference temperature and pressure, and no correction for them is made here.
- It is not a demand or code-compliance calculation. Plumbing codes size supplies from fixture units and diversity tables and set minimum flow rates at outlets; a single converted flow figure does not substitute for that, and does not confirm any fixture, appliance or supply meets its required rate.
Add the equipment this sizes
This result is a specification — 37.85 L/min — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations2
- 1 US liquid gallon = 231 cubic inches = 3.785411784 L exactly
- 1 imperial gallon = 4.54609 L, roughly 20% larger than a US gallon
Cite this page
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Pump curves, fixture ratings and design flows cross this boundary whenever equipment is sourced internationally. The conversion itself is exact, but the gallon is not a single unit: the US liquid gallon is 3.785 litres while the imperial gallon is 4.546, and a figure converted with the wrong one is twenty percent adrift — comfortably enough to undersize a pump or overstate a fixture's delivery. Note too that flow is only one input to pipe sizing. The same litres per minute through an undersized bore produces velocity noise, erosion over time and a pressure drop that starves outlets further along, so the converted figure needs to be checked against velocity limits rather than used alone.