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Irrigation Pump Sizing Calculator

Work out irrigation pump sizing instantly with clear inputs, formula shown and shareable results.

About Irrigation Pump Sizing Calculator

One acre-inch of water is 27,154 gallons, so area times application depth gives the daily volume directly. Dividing by the minutes the system runs gives the flow the pump must sustain, and the sprinkler operating pressure converted to feet of head sets the duty point.

Formulas

Daily volume

Gallons = acres x inches x 27154

Flow and power

GPM = gallons / (hours x 60); hp = GPM x head / 3960

Worked example

With the default values below, Irrigation Pump Sizing Calculator returns Pump flow required of 37.7. Change any input above and every figure here is recalculated in your browser.

Inputs used

Irrigated areaminimum 0.01 acres
2 acres
Daily application depthminimum 0.01 in/day
0.25 in/day
Operating hours per dayminimum 0.5 h
6 h
System pressure requiredminimum 1 psi
45 psi

Results

Pump flow required
37.7 GPM
Daily water volume
13,577 gal
Pressure head
103.8 ft
Hydraulic power
0.99 hp

Step by step

  1. 1Values used
  2. 2Daily volume
  3. 3Flow and power
  4. 4Pump flow required= 37.7 GPM
  5. 5Daily water volume= 13,577 gal
  6. 6Pressure head= 103.8 ft
  7. 7Hydraulic power= 0.99 hp

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Irrigation Pump Sizing figure worked out?

Gallons = acres x inches x 27154. One acre-inch of water is 27,154 gallons, so area times application depth gives the daily volume directly.

Should I allow for distribution losses?

Yes. Divide the gross application by the system's distribution uniformity, typically 0.75 for sprinklers and 0.90 for drip, otherwise the driest part of the field is under-watered.

What values do I need to enter?

This calculator takes 4 inputs: Irrigated area, Daily application depth, Operating hours per day, System pressure required. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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