Gallons Per Minute Calculator — GPM Flow Rate
Enter the volume of liquid (in US gallons) and the time it took to flow, and instantly get the flow rate in GPM, litres per minute (LPM), gallons per hour (GPH) and litres per hour.
US gallons
Time unit
US gallons per minute
- 1
Litres per minute (LPM)
10 GPM × 3.785 = 37.8541 US gallon = 3.785 litres. - 2
Flow rate (GPM)
50 gal ÷ 5 min = 10
How does this calculator work?
GPM = Volume (gallons) ÷ Time (minutes). Measure by timing how long it takes to fill a known container. Multiply GPM by 3.7854 for LPM, or by 60 for GPH. A standard faucet runs 1.5–2.5 GPM; a garden hose 5–15 GPM; a residential main up to 20 GPM.
Formula
How this is calculated
Gallons per minute (GPM) is the standard US measure of volumetric flow rate — how many gallons of liquid pass a point in one minute. It is used to size water pumps, irrigation systems, fire-suppression lines and residential plumbing. The calculation is simply the total volume delivered divided by the elapsed time. To measure GPM at home, fill a bucket of known size and time how long it takes; enter those two numbers above.
Typical reference points: a kitchen faucet runs at 1.8–2.5 GPM (the EPA WaterSense limit for efficient faucets is 1.5 GPM), a shower uses about 2–2.5 GPM, a garden hose delivers 5–15 GPM, and a standard residential supply main handles up to 15–20 GPM. Commercial and agricultural systems can reach hundreds or thousands of GPM.
To convert GPM to litres per minute (LPM), multiply by 3.7854 — the exact number of litres in a US liquid gallon. Multiplying by 60 converts to gallons per hour (GPH) or litres per hour (LPH). All calculations use US liquid gallons; if your volume is in litres, divide by 3.7854 to convert to gallons first.
Frequently asked questions
Fill a 5-gallon bucket with the hose and time how long it takes in seconds. Then GPM = 5 ÷ (seconds ÷ 60). For example, if it takes 30 seconds: GPM = 5 × 60 ÷ 30 = 10 GPM. Enter 5 gallons and 30 seconds above for the same result.
Add up the GPM rating for every sprinkler head or drip emitter that will run at the same time. That total is the minimum GPM your pump and supply line must deliver at your operating pressure. A drip system might need 0.5–2 GPM; a lawn sprinkler system can need 15–30 GPM.
Multiply GPM by 3.7854, since 1 US liquid gallon equals exactly 3.785411784 litres. So 10 GPM = 37.85 LPM. Divide by 3.7854 to go the other way.
Also known as
TG we-Calculate Editorial Team. (2026). Gallons Per Minute Calculator — GPM Flow Rate [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/gallons-per-minute-calculator
TG we-Calculate Editorial Team. "Gallons Per Minute Calculator — GPM Flow Rate." TG we-Calculate. 2026. https://we-calculate.com/calculator/gallons-per-minute-calculator.
TG we-Calculate Editorial Team, "Gallons Per Minute Calculator — GPM Flow Rate," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/gallons-per-minute-calculator
@misc{wecalculate_gallons_per_minute_calculator, title = {Gallons Per Minute Calculator — GPM Flow Rate}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/gallons-per-minute-calculator}}, year = {2026}, note = {TG we-Calculate} }
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