Sprinkler Head Spacing & Coverage Calculator
Calculate optimal sprinkler head spacing, total coverage area, number of heads required, and precipitation rate for your irrigation system.
Recommended: 50% (head-to-head coverage)
Formulas Used
Head Spacing:
S = D × (1 − Overlap%) where D = 2r (diameter)
At 50% overlap (head-to-head): S = r
Coverage Area per Head (Sector):
A = (θ / 360°) × π × r²
Precipitation Rate:
PR (in/hr) = (GPM × 96.25) / (SL × SW)
where 96.25 is the unit conversion factor (gal/min → in/hr over ft²)
Number of Heads:
NL = ⌈Length / S⌉ + 1 | NW = ⌈Width / S⌉ + 1
Total = NL × NW
Time to Apply 1 Inch:
T (min) = 60 / PR
Assumptions & References
- Head-to-head coverage (50% overlap) is the industry standard for uniform distribution per ASABE and IRRIGATION ASSOCIATION guidelines.
- The precipitation rate formula uses the conversion: 1 GPM over 1 ft² = 96.25 in/hr (derived from 1 gallon = 231 in³).
- Heads are assumed to be arranged in a square or rectangular grid pattern.
- Wind, pressure variation, and slope effects are not accounted for in this calculator.
- Distribution uniformity estimate is based on overlap percentage; actual CU should be verified with catch-can tests (ASABE S398).
- Recommended operating pressure for most pop-up spray heads: 25–30 PSI; rotary heads: 30–45 PSI.
- Reference: Irrigation Association, Landscape Irrigation Best Management Practices; ASABE Standard S436.