Sprinkler Head Spacing Calculator
Determine how many sprinkler heads you need and how to space them for complete, uniform coverage of any irrigation zone. Use it when designing a new system or diagnosing dry spots in an existing one.
Last updated: September 2026
Formula below · 2 sources (usda.gov, Wikipedia) · Updated Sep 2026
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About this calculator
Proper sprinkler head spacing ensures every part of a lawn receives water from at least two heads. Overlap is expressed as head spacing relative to the wetted diameter: 50% overlap means heads are spaced at 50% of the diameter, a distance equal to the throw radius (head-to-head coverage); 55% puts them at 0.9 × radius and 60% at 0.8 × radius. So spacing S = 2 × headRadius × (1 − overlap). Heads are placed at both edges of the zone and every S in between, giving ⌈areaLength ÷ S⌉ + 1 heads along the length and ⌈areaWidth ÷ S⌉ + 1 rows. The formula is: heads = (⌈areaLength ÷ S⌉ + 1) × (⌈areaWidth ÷ S⌉ + 1) for a square grid. Corner heads are quarter-circle, edge heads half-circle and interior heads full-circle.
How to use
Say your irrigation zone is 30 ft long by 20 ft wide, each head has a 10 ft radius, and you want 50% overlap (head-to-head). Spacing S = 2 × 10 × (1 − 0.5) = 10 ft. Heads along the length = ⌈30 ÷ 10⌉ + 1 = 4; rows = ⌈20 ÷ 10⌉ + 1 = 3. Total = 4 × 3 = 12 heads: 4 quarter-circle corner heads, 6 half-circle edge heads and 2 full-circle heads in the middle.
Frequently asked questions
How far apart should sprinkler heads be spaced for full lawn coverage?
The industry standard is head-to-head spacing, meaning each sprinkler head is placed no farther apart than its throw radius — not its full diameter. For a head with a 10 ft radius, you'd space heads up to 10 ft apart so adjacent coverage circles overlap significantly at their edges. This overlap is critical because precipitation rates drop toward the outer edge of a sprinkler's arc, and overlapping patterns average out to uniform coverage. In practice, slightly less than head-to-head spacing (85–90 % of radius) is recommended to compensate for wind interference.
What percentage of overlap should sprinkler heads have for uniform irrigation?
Most irrigation designers specify 50–60 % overlap between adjacent sprinkler heads to achieve distribution uniformity (DU) above 70 %, which is the threshold for healthy turfgrass. At 50 % overlap, the center of each head's throw reaches exactly to the adjacent head — the classic head-to-head standard. Increasing overlap to 60 % adds redundancy that compensates for pressure fluctuations and wind, but requires more heads. Less than 40 % overlap typically creates dry strips between heads that become visible as brown streaks within a few weeks of installation.
How do I choose between full-circle, half-circle, and quarter-circle sprinkler heads?
The choice depends on where in the irrigation zone each head is placed. Full-circle (360°) heads are used in the interior of a lawn where water can be thrown in all directions without hitting structures or paving. Half-circle (180°) heads are positioned along straight edges — fences, sidewalks, or driveways — so water is thrown inward only. Quarter-circle (90°) heads go in corners. Mixing patterns correctly is essential: a full-circle head in a corner would water the neighboring yard and waste half its output. Most modern pop-up heads have adjustable arc settings, making it easy to set the exact coverage angle needed for each location.