Multiply US gpm × 0.227125 to get m³/h, or m³/h × 4.402868 to get US gpm. For litres per minute, US gpm × 3.785412 = L/min and L/min × 0.06 = m³/h. Check which gallon your datasheet uses: a UK (imperial) gpm is 1.20095 US gpm.
Flow rate unit converter
Exact definitions: US gallon = 231 in³ = 3.785 411 784 L; UK gallon = 4.546 09 L; ft³ = 28.316 846 592 L; barrel = 42 US gallons. Results are rounded to 6 significant figures. Volume flow units only — mass flow (kg/h, lb/h) needs the fluid density.
How do you convert GPM to m³/h?
Multiply US gallons per minute by 0.227125. One US gallon is exactly 3.785 411 784 litres, so one gallon per minute is 3.785 411 784 L/min; multiplying by 60 min/h and dividing by 1000 L/m³ gives 0.227 124 707 m³/h.
US gpm → m³/h: Qm³/h = Qgpm × 3.785 411 784 × 60 ÷ 1000 = Qgpm × 0.227 125
m³/h → US gpm: Qgpm = Qm³/h × 4.402 868
L/min → m³/h: Qm³/h = QL/min × 0.06 · L/s → m³/h: × 3.6
UK gpm → US gpm: × 1.200 950 (4.546 09 ÷ 3.785 411 784)
Flow unit conversion map
GPM, m³/h and L/min conversion table
| US gpm | m³/h | L/min | L/s |
|---|---|---|---|
| 1 | 0.2271 | 3.785 | 0.0631 |
| 5 | 1.136 | 18.93 | 0.315 |
| 10 | 2.271 | 37.85 | 0.631 |
| 25 | 5.678 | 94.64 | 1.577 |
| 50 | 11.36 | 189.3 | 3.155 |
| 100 | 22.71 | 378.5 | 6.309 |
| 250 | 56.78 | 946.4 | 15.77 |
| 500 | 113.6 | 1 893 | 31.55 |
| 1 000 | 227.1 | 3 785 | 63.09 |
Is a GPM a US or a UK gallon?
In North American datasheets and pump curves, gpm means US gallons per minute unless stated otherwise. UK and some Commonwealth documents may use imperial gallons (4.546 09 L), which are about 20 % larger, so 100 UK gpm = 120.1 US gpm = 27.28 m³/h. If a document says only "gpm" and comes from the UK, confirm which gallon it uses before sizing a pipe or a meter.
Worked examples
| Convert | Calculation | Result |
|---|---|---|
| 100 US gpm to m³/h | 100 × 0.227125 | 22.71 m³/h |
| 50 m³/h to US gpm | 50 × 4.402868 | 220.1 US gpm |
| 250 L/min to US gpm | 250 ÷ 3.785412 | 66.04 US gpm |
| 500 L/min to m³/h | 500 × 0.06 | 30.0 m³/h |
| 100 UK gpm to m³/h | 100 × 4.54609 × 0.06 | 27.28 m³/h |
What do small-pipe flow meter ranges look like in m³/h and gpm?
Meter datasheets often give ranges in only one unit. The table converts the published upper flow limits of the SEGMENsensor U12 one-piece clamp-on ultrasonic flow meter (DN15–DN65) from L/min — the unit printed on the datasheet — into m³/h and US gpm.
| Pipe size | U12 upper limit (datasheet, L/min) | m³/h (calculated) | US gpm (calculated) |
|---|---|---|---|
| DN15 | 60 | 3.6 | 15.9 |
| DN20 | 100 | 6.0 | 26.4 |
| DN25 | 200 | 12.0 | 52.8 |
| DN32 | 300 | 18.0 | 79.3 |
| DN40 | 400 | 24.0 | 105.7 |
| DN50 | 600 | 36.0 | 158.5 |
| DN65 | 1 000 | 60.0 | 264.2 |
L/min values from the U12 datasheet; m³/h and gpm are calculated conversions, not additional ratings. The U13 small-pipe meter (DN15–DN40) is specified from 0.55–60 L/min on DN15 (0.033–3.6 m³/h, 0.15–15.9 US gpm) up to 2.5–400 L/min on DN40 (0.15–24 m³/h, 0.66–105.7 US gpm). For larger pipes, the U10 series covers velocities of ±0.03–±5 m/s and the U11 ±0.01–±12 m/s; flow rate then depends on pipe bore.
Compare the models in clamp-on ultrasonic flow meter models compared, check mounting rules in how to install a clamp-on flow meter, or see data center cooling water flow monitoring for m³/h-based loop sizing. Converting pressure as well? Use the pressure unit converter.
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Frequently Asked Questions
1 US gallon per minute is 0.227 125 m³/h (3.785 411 784 L × 60 ÷ 1000). One UK (imperial) gallon per minute is 0.272 765 m³/h.
Multiply m³/h by 4.402 868 to get US gpm, or by 3.666 154 to get UK gpm. Example: 50 m³/h = 220.1 US gpm.
Multiply US gpm by 3.785 412 (exact gallon definition). 10 US gpm = 37.85 L/min; divide L/min by 60 for L/s.
The gallon. A US gallon is 3.785 411 784 L, an imperial gallon 4.546 09 L, so 1 UK gpm = 1.200 95 US gpm. Mixing them up gives a 20 % sizing error.
Multiply by 0.06 (60 minutes per hour ÷ 1000 litres per cubic metre). 400 L/min = 24 m³/h.
Only with the fluid density. Mass flow = volume flow × density; for water near 20 °C (about 998 kg/m³), 1 US gpm ≈ 226.7 kg/h. Volume units such as gpm and m³/h convert directly; mass units do not.