Convert gal/min to L/min US gallons per minute ↔ litres per minute Free Online Secure
Type a value in US gallons per minute and read it in litres per minute at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Convert to litres per minute
Common values — Convert gal/min to L/min (US gallons per minute ↔ litres per minute)
| gal/min | L/min |
|---|---|
| 1 | 3.785411784 |
| 2 | 7.570823568 |
| 3 | 11.356235352 |
| 5 | 18.92705892 |
| 10 | 37.85411784 |
| 20 | 75.70823568 |
| 50 | 189.2705892 |
| 100 | 378.5411784 |
Where these units come from
Flow rate has no unit of its own either: it is a volume divided by a time, so each trade kept the volume it already used and attached whichever time suited the scale of the job. Litres per minute came from taps, pumps and anything a person watches fill; cubic metres per hour from water utilities, ventilation and irrigation, where a minute is too short to be useful; US gallons per minute from American plumbing, fire codes and well pumps. The numbers look very different for the same stream — one litre per minute is 0.06 cubic metres per hour — which is why a pump quoted in one unit and a pipe sized in another is a common source of expensive mistakes.
Where you meet them
A shower head delivers around 9 litres per minute, a garden hose roughly twice that, a domestic boiler is rated by how many litres a minute it can raise by a given temperature. Cubic metres per hour price water, size ventilation ducts and rate industrial pumps. Gallons per minute appear on American pump labels, sprinkler systems and fire hydrant specifications.
Questions people ask
Which gallon does gallons per minute mean here?
The US gallon, 3.785411784 litres. An imperial gallon per minute would be about a fifth larger, so a British figure quoted in gpm and read as American understates the flow by about a sixth. Pump and sprinkler data sheets rarely say which they mean, so check the country of origin before trusting a conversion in either direction.
Is a higher flow rate the same as higher pressure?
No, and confusing them is how showers get ruined. Pressure is the push; flow is how much actually moves. A narrow pipe at high pressure can deliver less water than a wide pipe at low pressure. Pumps are specified by both together — a curve showing what flow they achieve at each pressure — because neither number means much on its own.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Gallons per minute to litres per minute: living with American plumbing
Whoever buys an American tankless water heater, a motorhome, a hot tub or a set of plumbing fittings runs into the gallon per minute. The rating on the box says 5 gpm, the shower head says 2.5 gpm, the pump says 3.5 gpm, and the water in your own pipes is measured in litres. A reader in Europe, Australia or Canada who wants to know whether the appliance will keep up with the household must turn gal/min into L/min. To convert gal/min to L/min, multiply by 3.785: 2.5 gal/min is 9.46 L/min, 5 gal/min is 18.9 L/min and 12 gal/min is 45.4 L/min. The gallon is the US gallon. The calculator above multiplies as you type, and the sections that follow show what the figures mean for fixtures, water heaters, pipes and roofs.
Below come the rule with examples, short notes on each unit, a side-by-side look and a long series of household and building cases, ending with the slips people make most. Everything is computed locally in the page. For anything attached to a mains supply or a gas line, use a licensed installer.
How to convert gal/min to L/min: multiply by 3.785
The rule
A US gallon holds 3.785412 litres, which makes one gallon per minute 3.785412 litres per minute. For a “convert gal/min to L/min” calculation, take the gal/min figure times 3.785: 1.5 gives 5.68 L/min, 8 gives 30.3 L/min and 40 gives 151.4 L/min. To go the other way multiply L/min by 0.2642.
Two kinds of gallon
The imperial gallon of 4.546 litres lingers in older British and Commonwealth documents. A flow of 10 imperial gal/min is 45.5 L/min, while 10 US gal/min is 37.9. American appliance labels always use the US gallon, as does this page.
Worked examples
A kitchen faucet at 2.2 gal/min delivers 8.33 L/min. A hot-tub pump at 50 gal/min delivers 189 L/min. A tankless water heater rated for 5 gal/min delivers 18.9 L/min. A garden hose at 9 gal/min delivers 34.1 L/min.
A quick sanity test
Expect the L/min result to be nearly four times the gallon figure. A smaller number than you began with means 0.2642 was used where 3.785 belonged.
Gallons per minute
How American homes are plumbed
The gallon per minute is the unit of flow in US building codes, appliance ratings and manufacturers' data. Pressure comes with it in psi and pipe sizes in inches, so a whole system is described in a single set of customary units.
Where it appears
Appliance labels, plumbing codes, water-heater ratings and pump specifications.
Litres per minute
How the rest of the world measures it
The litre per minute is the everyday unit for taps, showers and domestic pumps in most countries. Larger flows move to litres per second or to cubic metres per hour.
Where it appears
Product data in Europe, Australia and elsewhere, and plumbing design in metric countries.
gal/min set beside L/min
Counted in litres, the same flow looks almost four times bigger than in gallons: 4 gal/min becomes 15.1 L/min and 30 gal/min becomes 114 L/min. The water is identical, and only the measuring cup changes.
Nothing is lost on the way. The mistake that shows up most is the US gallon taken for the imperial one, which is 20 per cent off.
Where the conversion shows up
Tankless water heaters
American tankless heaters are rated by the flow they can heat by a given rise, for example 5 gpm at a 35 °F rise. The power needed is gpm × 500 × rise in °F, so 5 × 500 × 35 = 87,500 BTU/h, 25.6 kW. In metric terms the flow is 18.9 L/min at a rise of 19.4 °C. Bring the rise down to 25 °C and the same heater gives 14.7 L/min. A “convert gal/min to L/min” calculation gives the first half of the comparison, and the temperature rise gives the other half.
Pipes and velocity
Water in a domestic pipe should run at no more than about 1.5 m/s to keep noise down. A 20 mm bore pipe at 1.5 m/s carries 28.3 L/min, 7.5 gal/min. That is roughly what a 3/4-inch copper line delivers at 5 ft/s. Doubling the diameter quadruples the flow at the same speed.
Roof drainage
Rain falling at 1 inch an hour on 1,000 square feet of roof makes 623 gallons an hour, 10.4 gal/min, which is 39.3 L/min. Gutter and downpipe capacity in the US is given in gpm for a design rainfall rate, so it is useful to know the metric equivalent when you compare it with a roof in mm per hour.
The flow rate behind a tankless heater
The same relationship works for any rise. Heating 38 L/min, 10 gal/min, by 20 °C needs 53 kW, which is 181,000 BTU/h. This is why a single large tankless heater struggles to run two showers at once in winter, when the incoming water is cold and the rise is large.
Ponds and waterfalls
A garden waterfall needs about 100 gallons an hour for each inch of weir width, 1.7 gpm per inch, so a 24 inch weir requires 40 gpm, 151 L/min. Pond pumps are sold in gallons per hour and lose capacity with height: a 2,000 gph pump may deliver much less than that at 6 feet of head.
Swimming pool plumbing
Residential pool plumbing is designed for a velocity of about 8 feet per second in suction lines. A two-inch pipe at that speed carries about 84 gal/min, 317 L/min. A pump of 60 gpm fills a 20,000 gallon pool, 75.7 cubic metres, in a turnover of 5.6 hours. A “convert gal/min to L/min” calculation on the pump rating gives the same pump as 227 L/min for a European filter.
Reading a pump curve
An American pump curve plots gpm on the horizontal axis and feet of head on the vertical one. A point of 20 gpm at 80 ft is 75.7 L/min at 24.4 metres. Many curves also show efficiency, so the best point is read at the top, and the pump should be picked to run near it.
Gallons per hour and per day
Small pumps and metering devices use gallons per hour, gph, and treatment systems gallons per day, gpd. 300 gph is 5 gpm, 18.9 L/min, and 100 gpd is 0.069 gpm, 0.26 L/min. Divide gph by 60 and gpd by 1,440 before you convert.
Fire sprinklers in a home
A residential sprinkler system is designed to flow about 13 to 26 gpm per head, 49 to 98 L/min, for a duration, so the domestic main must supply this in addition to normal use. Flow tests of a hydrant, in gpm at a residual pressure, give the supply side. A “convert gal/min to L/min” calculation turns the test report into the metric terms used in a European design.
Ice makers and refrigerator feeds
A refrigerator water line passes about 0.5 gal/min, 1.9 L/min, to fill the ice maker and the dispenser. A water filter in that line must be rated above this flow. A filter that restricts the line to 0.2 gpm, 0.76 L/min, makes the dispenser slow.
Commercial dishwashing and food service
A conveyor dishwasher uses 0.9 gallons per rack, and a pre-rinse spray valve runs at 1.6 gpm, 6.06 L/min. A hose reel in a kitchen can deliver 5 gpm, 18.9 L/min. These numbers are small, yet a busy restaurant uses several thousand litres of water a day.
Car wash and pressure cleaning
A pressure washer rated 2.5 gpm at 2,000 psi is 9.46 L/min at 138 bar. It has hydraulic power of 2.2 kW, about 2.9 hp. A cold-water gas machine of 4 gpm at 4,000 psi, 15.1 L/min at 276 bar, has 7.0 kW, 9.3 hp, so it needs an engine of 12 hp or more.
A worked example
You want an American tankless heater for a European house. It is rated 7 gpm at a 40 °F rise, which is 26.5 L/min at 22.2 °C. A shower of 9 L/min mixed at 38 °C from 10 °C supply needs about 5.6 L/min of water heated to 55 °C. Two showers at once need 11.2 L/min. At a 45 °C rise the heater's output falls to 13.1 L/min, still above that.
The mental shortcut
To convert gal/min to L/min without a calculator, quadruple the figure and subtract 5 per cent of the result. For 10 gal/min: 40 less 2 is 38 L/min, close to the exact 37.85. Quadrupling alone would be 5.7 per cent too high.
Recreational vehicles
A fresh-water pump in a motorhome is rated 3.0 gpm, 11.4 L/min, at 55 psi, 3.8 bar. A marine-style pump of 5.0 gpm gives 18.9 L/min. With a fresh-water tank of 40 gallons, 151 litres, a single tap at 1 gpm drains the tank in 40 minutes, so the water supply is the limiting factor on a long trip.
Spreadsheet formulas
Put the gal/min in column A, then =A2*3.785412 in column B gives L/min and =A2*0.2271247 gives m³/h. The reverse is =B2*0.264172. A helper column of =A2*0.0630902 returns litres per second for a cross-check.
Rounding in home specifications
Home appliance flows are given to a tenth of a gallon at best, and pressure variations change them by 10 per cent anyway. 2.5 gal/min is 9.5 L/min, not 9.4635. Give metric values to one decimal place for taps and to whole litres for pumps.
Landmarks to memorise
1 gal/min is 3.79 L/min. 2 gal/min is 7.57 L/min. 5 gal/min is 18.9 L/min. 10 gal/min is 37.9 L/min. 25 gal/min is 94.6 L/min. 100 gal/min is 379 L/min. With these landmarks nearly every mental convert gal/min to L/min is possible.
Reference ladder
0.25 gal/min: 0.95 L/min. 1.2 gal/min: 4.54 L/min. 3 gal/min: 11.4 L/min. 9 gal/min: 34.1 L/min. 20 gal/min: 75.7 L/min. 60 gal/min: 227 L/min. 150 gal/min: 568 L/min. With a list of this kind any result can be checked quickly.
Checking by reversing
Test a “convert gal/min to L/min” calculation answer by dividing it by 3.785: 75.7 L/min gives 20.0 gal/min, so the 20 you started from came through intact. A second sign of a good result is that the L/min number is almost four times the gallon one.
Link to cubic metres per hour and litres per second
In one gallon per minute there are 3.785 L/min, 0.2271 m³/h and 0.0631 L/s. For 50 gpm that makes 189 L/min, 11.4 m³/h and 3.15 L/s. The units differ and the flow does not, so a “convert gal/min to L/min” calculation only relabels it.
Two routes to one answer
Go straight to L/min with 3.785, or travel via cubic metres an hour: gal/min × 0.2271 × 16.67. A further path uses litres per second, gal/min × 0.0631 × 60. If the answers drift apart, a digit slipped somewhere.
Hot tubs and spas
A spa pump has two speeds, perhaps 25 gpm, 95 L/min, for filtering and 80 gpm, 303 L/min, for the jets. A 400 gallon tub, 1,514 litres, is filtered in 16 minutes at low speed. Each jet takes 8 to 15 gpm, 30 to 57 L/min, so a spa with 20 jets needs the pump on high.
Garden hoses
A 5/8 inch hose at 40 psi delivers about 9 gal/min, 34.1 L/min. A 3/4 inch hose gives about 15 gpm, 56.8 L/min, while a 1/2 inch hose gives only 4 gpm, 15.1 L/min, and a “convert gal/min to L/min” calculation on each shows the gap at once. Length matters too: 100 feet of hose at 5/8 inch loses a noticeable part of its flow compared with 25 feet.
Sump pumps
A sump pump rated 2,000 gallons an hour at 10 feet of lift is moving 33 gal/min, 126 L/min. In a heavy storm a basement might need 50 gpm, 189 L/min, so the pump should be sized for the peak. A “convert gal/min to L/min” calculation puts the pump on the same scale as the pit's inflow.
Dishwashers and washing machines
An American front-loading washing machine fills at 2 to 3 gpm, 7.6 to 11.4 L/min, and uses 12 to 20 gallons a cycle, 45 to 76 litres. A dishwasher fills at about 2 gpm and takes 4 to 6 gallons, 15 to 23 litres. The flow only matters if the water supply is weak, because the cycle volume is what is billed.
Home water demand at peak
A house with two bathrooms may demand 8 gpm at the busiest time, 30.3 L/min, when a shower, a kitchen tap and a washing machine run together. A four-bathroom house can ask for 15 gpm, 56.8 L/min. The water main and the meter must supply the peak, not the average.
Water meters
A residential meter in the US is a 5/8 inch model that handles up to 20 gpm, 75.7 L/min, continuously. The nearest European size, a DN15 with Q3 = 2.5 m³/h, flows 41.7 L/min, 11 gpm, at its rating. The American meter is sized for a higher maximum, and each reads in its own units.
Pressure and flow
An outlet that gives 9 gpm at 40 psi will give about 12.7 gpm at 80 psi, because flow rises with the square root of pressure. In metric terms, 34 L/min at 2.8 bar becomes 48 L/min at 5.5 bar. Doubling the pressure raises the flow by only 41 per cent.
More values for convert gal/min to L/min
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 gal/min = 0.3785411784 L/min
- 0.5 gal/min = 1.892705892 L/min
- 3 gal/min = 11.356235352 L/min
- 4 gal/min = 15.141647136 L/min
- 7 gal/min = 26.497882488 L/min
- 15 gal/min = 56.78117676 L/min
- 20 gal/min = 75.70823568 L/min
- 75 gal/min = 283.9058838 L/min
- 200 gal/min = 757.0823568 L/min
- 500 gal/min = 1,892.705892 L/min
- 2,000 gal/min = 7,570.823568 L/min
- 10,000 gal/min = 37,854.11784 L/min
Common slips with a “convert gal/min to L/min” calculation
Dividing instead of multiplying
From gal/min to L/min the number gets larger. If 10 gal/min became 2.6, you used the factor for the other direction.
US and imperial gallons
Convert with 3.785 for a US gallon and 4.546 for an imperial one. A flow of 10 gal/min is 37.9 L/min in the US system and 45.5 L/min in the imperial.
Flow at a given pressure
A pump or tap has no single flow. The figure is valid at one pressure or head, so quote it together with the pressure when you compare two products.
Short answers
How do I convert gal/min to L/min?
Take the gallons per minute times 3.785.
What is 10 gal/min in L/min?
It is 37.9 L/min.
What is 2.5 gal/min in L/min?
It is 9.46 L/min.
What is 100 L/min in gal/min?
It is 26.4 gal/min.
Is my number sent anywhere?
No, everything is computed in the browser.
More pages and a wrap-up
Other flow conversions are listed in Convert m³/h to L/min, Convert L/min to m³/h, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert ft to mi, Convert cm to mm, Convert dm to m. Going the other way is covered by Convert L/min to gal/min.
To sum up, a “convert gal/min to L/min” calculation needs one multiplication by 3.785 and a unit beside the answer. The figure is worked out on your own device, without registration or upload.