How this calculator works
Divide collected volume by elapsed time to obtain average volumetric flow. The main GPM figure uses US liquid gallons, while a separate figure reports imperial gallons per minute. Volume inputs support both gallon definitions. Reverse fill-time and delivered-volume calculations assume flow stays constant during the interval; a timed collection measures average flow even when it fluctuates.
Formula
Q = V / t; V = Q x t; t = V / Q; US GPM = Q(m3/s) x 60 / 0.003785411784; imperial GPM = Q(m3/s) x 60 / 0.00454609.
Worked example
Collecting 100 US gal in 4 minutes gives 25 US GPM. A constant 10 US GPM delivered for 30 minutes supplies 300 US gal, or 1135.6235 L.
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Frequently asked questions
Does GPM always mean US gallons?
No. This page labels US and imperial results separately. Use the definition required by the equipment or local specification.
Can I use a bucket test?
Yes. Measure the actual collected volume and elapsed time. A longer sample can reduce timing error when flow is steady.
Does this calculate pump pressure?
No. Flow alone does not determine pressure, head loss or pump performance. Those also depend on the system and pump curve.