Sprinkler Head Coverage & Spacing Calculator
Calculate the coverage area per sprinkler head, recommended head spacing, and the total number of heads required to irrigate a rectangular zone.
Industry standard is 50% (head-to-head coverage). Higher % = more overlap.
Formulas Used
1. Coverage Area per Head (sector of a circle):
A = (arc° / 360) × π × r²
Where r = throw radius (ft), arc° = sprinkler arc angle.
2. Recommended Head Spacing:
S = 2 × r × (1 − overlap / 100)
At the industry-standard 50% overlap: S = r (head-to-head spacing equals the radius).
3. Number of Heads per Row / Column:
n_L = ⌈Zone Length / S⌉ n_W = ⌈Zone Width / S⌉
4. Total Heads:
N = n_L × n_W
5. Actual Spacing (evenly distributed):
S_actual_L = Zone Length / n_L S_actual_W = Zone Width / n_W
Assumptions & References
- The zone is assumed to be a flat rectangle with uniform water demand.
- Head-to-head coverage (50% overlap) is the industry standard recommended by the Irrigation Association (IA) and Rain Bird. It ensures uniform distribution uniformity (DU ≥ 0.70).
- Coverage area is calculated as a circular sector: A = (arc/360) × π × r².
- Heads are arranged in a square grid pattern. Triangular spacing can cover ~15% more area with the same number of heads but is not computed here.
- Throw radius values are manufacturer-rated at a specific operating pressure (typically 30–45 PSI). Actual radius varies with pressure — verify with manufacturer data sheets.
- Wind, slope, and soil infiltration rate are not accounted for in this calculator.
- For precipitation rate (in/hr), use: PR = (96.25 × GPM) / S² once flow rate per head is known (Hunter Industries, 2023).
- Reference: Rain Bird Irrigation Design Manual; Hunter Industries Residential Irrigation Design Guide; Irrigation Association Best Management Practices.