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Sprinkler Coverage Calculator

Work out sprinkler coverage instantly with clear inputs, formula shown and shareable results.

About Sprinkler Coverage Calculator

A rotating sprinkler wets a circle, but heads must overlap to give even coverage — spacing is set at 50-60% of the wetted diameter, so each head is credited with a square of side (2 x radius x spacing factor). Application rate is nozzle flow divided by that square, in mm/hour, and must stay below the soil infiltration rate to avoid runoff.

Formulas

Spacing and coverage

Spacing = 2 x radius x spacing%; area per head = spacing^2

Application rate

Rate (mm/h) = flow (L/min) x 60 / area per head (m2)

Worked example

With the default values below, Sprinkler Coverage Calculator returns Sprinkler Heads Required of 23. Change any input above and every figure here is recalculated in your browser.

Inputs used

Sprinkler Throw Radiusminimum 0.5 m
12 m
Head Spacing As % Of Diameteraccepts 30–100 %
55 %
Nozzle Flow Rateminimum 0.1 L/min
25 L/min
Field Areaminimum 1 m2
4,000 m2

Results

Sprinkler Heads Required
23
Head-To-Head Spacing
13.20
Area Covered Per Head
174.24
Application Rate
8.61

Step by step

  1. 1Values used
  2. 2Spacing and coverage
  3. 3Application rate
  4. 4Sprinkler Heads Required= 23
  5. 5Head-To-Head Spacing= 13.20
  6. 6Area Covered Per Head= 174.24
  7. 7Application Rate= 8.61

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

Why not space heads a full diameter apart?

A single sprinkler applies far less water at the edge of its circle than near the head. Overlapping at 50-60% of diameter evens out the profile; wider spacing leaves dry rings between heads.

How high can the application rate be?

Keep it under the soil intake rate — roughly 25-50 mm/h for sand, 10-20 mm/h for loam and 4-10 mm/h for clay. Above that, water ponds and runs off instead of infiltrating.

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