Flow Rate Converter (L/min, gpm, m³/h, cfm)
Type in either box to turn L/min into gpm, m³/h into L/s, cfm into m³/h or any pair of flow units, with the answer in every unit at once.
Type in either box. Tap a unit under a box to change it.
Use the inside diameter, not the pipe’s nominal or outside size. A 1/2 in copper pipe is about 13.4 mm inside.
As a rough guide, water in home and building pipes usually runs at about 1–2.5 m/s (3–8 ft/s). Much faster gets noisy and wears the pipe, so a bigger pipe may be better.
Turn the tap or shower fully on, then time how long a bucket or jug of known size takes to fill.
Density in kg/m³. The buttons are typical figures at about 15–20 °C; fuels and milk vary a little from one batch to the next.
L/min to US gpm table
Common values both ways. Change the units above and the table follows.
| L/min | US gpm |
|---|---|
| 1 | 0.2641721 |
| 2 | 0.5283441 |
| 5 | 1.32086 |
| 10 | 2.641721 |
| 15 | 3.962581 |
| 20 | 5.283441 |
| 25 | 6.604301 |
| 30 | 7.925162 |
| 40 | 10.56688 |
| 50 | 13.2086 |
| 75 | 19.8129 |
| 100 | 26.41721 |
| 150 | 39.62581 |
| 200 | 52.83441 |
| 250 | 66.04301 |
| 500 | 132.086 |
| 750 | 198.129 |
| 1,000 | 264.1721 |
| US gpm | L/min |
|---|---|
| 1 | 3.785412 |
| 2 | 7.570824 |
| 5 | 18.92706 |
| 10 | 37.85412 |
| 15 | 56.78118 |
| 20 | 75.70824 |
| 25 | 94.63529 |
| 30 | 113.5624 |
| 40 | 151.4165 |
| 50 | 189.2706 |
| 75 | 283.9059 |
| 100 | 378.5412 |
| 150 | 567.8118 |
| 200 | 757.0824 |
| 250 | 946.3529 |
| 500 | 1,892.706 |
| 750 | 2,839.059 |
| 1,000 | 3,785.412 |
Typical flow rates (examples, not specs)
- Dripping tap, fast drip (typical)50 mL/min = 0.793 US gph = 3 L/h
- Low-flow shower head (typical)6 L/min = 1.59 US gpm = 0.36 m³/h
- Standard shower (typical)2.5 US gpm = 9.46 L/min = 0.568 m³/h
- Kitchen tap, fully open (typical)10 L/min = 2.64 US gpm = 0.6 m³/h
- Garden hose, 3/4 in (typical)40 L/min = 10.6 US gpm = 2.4 m³/h
- Home water main at the meter (typical)20 US gpm = 75.7 L/min = 4.54 m³/h
- Fire hose line (typical)150 US gpm = 568 L/min = 34.1 m³/h
- Bathroom extract fan (typical)50 ft³/min = 85 m³/h = 23.6 L/s
- Home central AC, 3 ton (typical, 400 cfm a ton)1,200 ft³/min = 2,040 m³/h = 566 L/s
- Medium oil well (generic)1,000 bbl/d = 110 L/min = 29.2 US gpm
- Small river, average (generic)10 m³/s = 36,000 m³/h = 159,000 US gpm
These are typical figures to give a feel for the numbers, not the rating of any tap, pump, fan or well. Check the product’s label or data sheet for its real flow.
How your flow rate is converted
Every unit goes into litres per second first, then out to the unit you want.
- 1
Your flow
100 L/min →
US gpm - 2
Into litres per second
100 × 0.01666667 =
1.666667 L/s - 3
Out to US gpm
1.666667 ÷ 0.0630902 =
26.41721 US gpm - 4
The shortcut
1 L/min =
0.2641721 US gpm
Read more: the formula, worked examples, pipe flow and speed, fill time, mass flow and the unit names
The formula
litres per second = your number × L/s in one of your unit
answer = litres per second ÷ L/s in one of the unit you want
L/min → US gpm: gpm = L/min ÷ 3.785411784
US gpm → L/min: L/min = gpm × 3.785411784
flow = π × inside diameter² ÷ 4 × speed
speed = flow ÷ (π × inside diameter² ÷ 4)
time to fill = volume ÷ flow
mass flow = flow × density
Worked example
100 L/min in US gpm. Into litres per second first: 100 ÷ 60 = 1.666667 L/s. One US gpm is 3.785411784 L ÷ 60 s = 0.0630902 L/s, so 1.666667 ÷ 0.0630902 = 26.41721 US gpm. In one step: 100 ÷ 3.785411784 = 26.41721. As a shortcut, 1 L/min = 0.2641721 US gpm.
The other way: 10 US gpm × 3.785411784 = 37.85412 L/min. And 6 m³/h × 1,000 ÷ 60 = 100 L/min.
Pipe flow and speed (Advanced)
With the defaults: a 50 mm pipe is 0.05 m across, so its area is π × 0.05² ÷ 4 = 0.0019635 m². At 1.5 m/s: 0.0019635 × 1.5 = 0.0029452 m³/s = 2.9452 L/s = 176.71 L/min (10.603 m³/h, 46.68 US gpm). In US units, a 2 in pipe at 4 ft/s carries 39.17 US gpm.
Speed from flow, with the defaults: 100 L/min = 0.0016667 m³/s. A 25 mm pipe has an area of π × 0.025² ÷ 4 = 0.00049087 m², so the water runs at 0.0016667 ÷ 0.00049087 = 3.3953 m/s (11.14 ft/s). That is fast for a home pipe; a 32 mm pipe brings it down to about 2.07 m/s.
Time to fill and the bucket test (Advanced)
1,000 L at 20 L/min takes 1,000 ÷ 20 = 50 minutes. A 10 L bucket that fills in 30 s means 10 L ÷ 0.5 min = 20 L/min, which is 5.283 US gpm or 4.399 UK gpm.
Mass flow (Advanced)
100 L/min of water at 1,000 kg/m³ (1 kg in every litre) is 100 kg a minute: 100 ÷ 60 = 1.6667 kg/s, 100 × 60 = 6,000 kg/h (6 t/h), and 100 ÷ 0.45359237 = 220.46 lb/min. Water at 1,000 kg/m³ weighs 8.345 lb per US gallon.
Unit names
| Unit | Also written | In L/min |
|---|---|---|
| US gpm | gpm, GPM, gal/min | 3.7854 |
| UK gpm | imperial gpm, igpm | 4.5461 |
| m³/h | m³/hr, cu m/h, cmh | 16.6667 |
| ft³/min | cfm, CFM, cu ft/min | 28.3168 |
| ft³/s | cfs, CFS, second-feet | 1,699.0108 |
| bbl/d | bpd, BOPD, bbl/day | 0.110408 |
| ac·ft/d | acre-ft/day, AF/d | 856.5846 |
| MGD | mgd, million US gallons a day | 2,628.7582 |
Volume flow or mass flow?
Everything in the converter is volume flow: how much space the liquid or gas takes up each second. Mass flow is how much it weighs, so it depends on the density. For gases this matters a lot, because a cubic foot of air holds much less air when it is warm or at altitude. For volumes on their own, use the volume converter; for a pipe’s own volume, the pipe volume calculator.
Factors are exact by definition: 1 US gallon = 231 in³ = 3.785411784 L, 1 UK (imperial) gallon = 4.54609 L, 1 ft = 0.3048 m (so 1 ft³ = 28.316846592 L), 1 in = 0.0254 m, 1 oil barrel = 42 US gallons = 158.987294928 L, 1 acre-foot = 43,560 ft³ = 1,233.48183754752 m³, 1 lb = 0.45359237 kg. A year here is 365 days. Checked 17 October 2026 against NIST Special Publication 811.
Common questions
How do I convert L/min to gpm?
Divide litres per minute by 3.785411784 to get US gallons per minute. So 100 L/min is 26.42 US gpm. For UK (imperial) gallons per minute, divide by 4.54609 instead: 100 L/min is 22.00 UK gpm.
How do I convert gpm to L/min?
Multiply US gpm by 3.785411784. So 10 gpm is 37.85 L/min. A quick rough check: multiply by 4 and take off a little (40 − 2 = 38).
How do I convert m³/h to L/min?
Multiply by 1,000 and divide by 60, which is the same as multiplying by 16.667. So 6 m³/h is 100 L/min. To get US gpm from m³/h, multiply by 4.4029.
What is cfm and how does it compare with L/s?
cfm is cubic feet per minute, the usual unit for fans, air ducts and compressors. 1 cfm = 28.317 L/min = 0.4719 L/s, so 100 cfm is 47.19 L/s or 169.9 m³/h. cfs (cubic feet per second) is 60 times bigger and is used for rivers.
How do I work out flow from pipe size and speed?
Flow = pipe area × speed, and the area of a round pipe is π × inside diameter² ÷ 4. A 50 mm pipe with water at 1.5 m/s carries 0.0019635 m² × 1.5 m/s = 0.002945 m³/s, which is 176.7 L/min. Advanced does this with mm or inches and m/s or ft/s, and the other way round too.
How do I measure the flow from my tap or shower?
Do a bucket test: time how long it takes to fill a bucket or jug of known size, then divide the volume by the time. A 10 L bucket that fills in 30 seconds means 10 ÷ 0.5 min = 20 L/min (5.28 US gpm). Advanced has a bucket test helper.
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