01
Formula
GPM = gallons ÷ minutes.
Head = static + friction + psi × 2.31. Hydraulic GPM = cubic inches per rev × RPM ÷ 231. Sprinkler inches per hour = 96.3 × GPM ÷ (spacing × spacing), with spacing in feet.
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GPM calculator for flow, head, and sprinklers
This GPM calculator divides gallons by minutes. Switch it to a pump head calculator, a hydraulic flow calculator, or a sprinkler calculator. The pump sizing calculator is the head mode: static lift plus friction plus pressure converted at 2.31 feet per psi. The irrigation calculator note on the sprinkler card shows how many gallons are in 5 acre-inches. The irrigation flow calculator and the water flow calculator are the gallons-per-minute mode.
Find
Flow
50.00gpm
Gallons500
Minutes10.00
Gallons per hour3,000
Planning estimate from the numbers you enter. Coverage, density, waste and price are assumptions, not a supplier quote or an engineering specification.
How it works
Gallons per minute is volume divided by time.
Five hundred gallons in 10 minutes is 50.00 gallons per minute, or 3,000 gallons per hour. Pump head in feet equals static lift plus friction loss plus psi times 2.31. Twenty feet of lift, 8 feet of friction, and 40 psi is 120.40 feet of head. Hydraulic flow equals cubic inches per revolution times RPM, divided by 231. A 2.5 cubic inch pump at 1,800 RPM moves 19.48 gallons per minute. Sprinkler precipitation in inches per hour equals 96.3 times gallons per minute, divided by the spacing in feet along the row times the spacing across. Two gallons per minute on a 20 by 20 foot spacing is 0.482 inches per hour. Five acre-inches of irrigation is about 135,771 gallons. That last figure is the volume of an inch of water on five acres. It is not a recommendation.
02
Example
500 gallons in 10 minutes.
The water flow calculator shows 50.00 GPM. The head example is 120.40 feet. The hydraulic example is 19.48 GPM. The sprinkler example is 0.482 inches per hour. Use the mode that matches the question.
03
Tips
Friction loss is an input, not a hidden table.
The pump head calculator will not guess pipe size and fittings. Use the pressure drop calculator for a Hazen-Williams loss, then type that loss here. The pump sizing calculator is only as good as that friction number.
04
Equipment
The pump is the machine.
Dengaro arranges financing for a pump. Flow and head are not a loan amount.
Important questions
Know what to expect.
What is 2.31 feet per psi?+
A psi of water pressure holds a column of water about 2.31 feet tall. The pump head calculator uses that to turn a required outlet pressure into feet of head.
How does the irrigation calculator use 5 acres?+
The sprinkler card shows the gallons in 5 acre-inches so you can see the volume behind an inch of water. Change the idea by scaling: one acre-inch is one fifth of that line. The irrigation flow calculator itself is the GPM mode.
Is 96.3 exact?+
It is the standard sprinkler constant when spacing is in feet and flow is in gallons per minute. The result is inches per hour on the area between the heads.
Can hydraulic flow size a cylinder?+
It gives pump flow from displacement and RPM. Cylinder speed is on the hydraulic cylinder calculator once that page is available. This hydraulic flow calculator stops at the pump.
Financing built into the sale