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LunaCalc

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Gallons Per Minute Calculator (GPM)

Calculate volumetric flow from a measured volume and elapsed time.

Calculator
US gal/min
L/min
m3/h

About this calculator

This flow-rate calculator converts a measured volume and elapsed time into gallons per minute, liters per minute, and cubic meters per hour.

Formula notes

GPM = volume in US gallons x 60 / elapsed time in seconds.

Worked examples

  1. Example: 5 US gallons collected in 30 seconds is 10 GPM, about 37.85 L/min.
  2. Collecting 2 cubic feet of water in 15 seconds equals about 59.84 GPM.

How to use it

  1. Enter the measured volume with its unit.
  2. Enter the elapsed collection time.
  3. Read GPM, L/min, and m3/h together.

Frequently asked questions

Which gallon is used for the output?

Outputs use US gallons; UK gallons are supported as an input and converted first.

Is the flow assumed constant?

Yes. The result is an average rate over the measured interval.

Limits and interpretation

  • The flow rate is an average over the measured interval; pulsating or variable flow needs a more detailed measurement.
  • Volume inputs use volumetric units at the stated conditions; temperature and pressure effects on density are not modeled.

References