Sprinkler Coverage Calculator

Sprinkler Coverage Inputs

Enter your site geometry, sprinkler radius, desired overlap, and flow limits. Then calculate coverage, head count, spacing, runtime, and exports.

Example Data Table

Use this sample as a quick reference for typical planning inputs.

Note: Units follow your selection. Replace values with site data.

Formula Used

• Project area: Rectangular = L x W. Circular = pi x (D/2)^2. Custom = entered area.
• Recommended spacing: S = 2R x (1 - overlap%). Triangular uses Y spacing = 0.866 x S.
• Area per head: Ahead = Sx x Sy.
• Estimated head count: N approx area / Ahead. Rectangular uses a grid estimate with edge allowance.
• Precipitation rate: Imperial: PR = 96.25 x GPM / Ahead. Metric: PR = (LPM x 60) / Ahead (mm/hr).
• Runtime: time = adjusted depth / PR. Adjusted depth = depth / efficiency%.
• Total flow: Qtotal = flow per head x N. Zones approx Qtotal / zone limit.

How to Use This Calculator

1. Select your unit system and area shape.
2. Enter site dimensions or the total custom area.
3. Choose a pattern and input sprinkler radius.
4. Set overlap percentage for wind and distribution.
5. Enter flow per head and target application depth.
6. Optionally set a zone flow limit and efficiency.
7. Press calculate to view results above the form.
8. Export results using the CSV and PDF buttons.

Sprinkler Coverage Planning Article

1) Why coverage planning matters

Uniform irrigation supports healthy turf and avoids dry spots that trigger reseeding or sod replacement. Overwatering increases runoff, stains paving, and can undermine subgrade near walkways. A simple coverage plan also helps estimate material quantities and labor hours before installation.

2) Radius, overlap, and spacing

Head-to-head coverage is a common rule because wind and pressure losses reduce throw at the edges. This calculator converts overlap into spacing using S = 2R x (1 - overlap). For example, a 15 ft radius at 50% overlap yields 15 ft spacing; at 40% overlap it becomes 18 ft.

3) Square versus triangular layouts

Square grids are straightforward to stake and align with rectangular lawns. Triangular layouts tighten the row spacing by 0.866x, which can improve uniformity for round patterns. The tradeoff is more complex set-out and sometimes a slightly higher head count.

4) Estimating head count and edge allowance

For rectangles, the tool estimates rows and columns and adds an edge allowance so corners are not ignored. If a 100 ft by 60 ft lawn uses 15 ft by 15 ft spacing, a typical estimate becomes 8 heads by 5 heads, or 40 total. Field staking can then refine boundary placement.

5) Precipitation rate as a performance check

Precipitation rate links nozzle flow to the area each head serves. In imperial units, PR (in/hr) = 96.25 x GPM / A_head. At 3 gpm and 225 sqft per head, PR is about 1.28 in/hr. High rates may require cycle-and-soak programming.

6) Runtime and efficiency adjustments

Real systems are not perfectly uniform, so distribution efficiency is used to avoid under-irrigation. If the target depth is 0.50 in and efficiency is 75%, the adjusted depth is 0.67 in. With a 1.28 in/hr rate, the runtime estimate is roughly 31 minutes.

7) Zone sizing and flow limits

Zones are usually constrained by available flow, pressure, and valve sizing. This calculator multiplies flow per head by the estimated head count and compares it to a zone flow limit. If total flow is 120 gpm and the limit is 15 gpm, the plan suggests about 8 zones.

8) Practical installation notes

Confirm static and dynamic pressure, then select nozzles with matched precipitation across different arcs. Keep similar head types on the same zone, minimize elevation swings, and avoid spraying buildings. After installation, perform a catch-can test and fine-tune runtime to measured performance.

FAQs

1) What overlap percentage should I start with?

Start with 50% for open areas. Increase overlap when wind exposure is high or pressure varies. Decrease overlap only when you are confident in pressure regulation and nozzle selection.

2) Is triangular spacing always better than square spacing?

Not always. Triangular patterns can improve uniformity for circular sprays, but they are harder to stake and may increase head count at boundaries. Choose the pattern that matches the site and crew workflow.

3) Why does the tool show a coverage ratio?

It compares estimated effective coverage to site area after applying efficiency. A ratio near 1.00 suggests the spacing and head count are reasonable. Below 0.95 indicates likely gaps; above 1.05 suggests extra overlap.

4) How do I choose flow per sprinkler?

Use nozzle charts at expected operating pressure and arc. Avoid mixing very different nozzle types on one zone. Enter a reasonable value, then refine after final nozzle selection and pressure testing.

5) What depth should I use for a single run?

Many turf schedules target roughly 0.25 to 0.75 inches per irrigation day, depending on soil and season. Use local guidance and soil infiltration rate, then split runtime into multiple cycles if runoff occurs.

6) How accurate is the runtime estimate?

It is a planning estimate based on precipitation rate and efficiency. Actual runtime depends on soil type, slope, shading, wind, and real pressure at the head. Verify using a catch-can test and adjust controller programming.

7) What should I do if zones exceed my flow limit?

Add more zones, lower nozzle flow, or split the area into smaller circuits. Confirm available flow at the connection and include pressure losses from long runs and elevation changes.