Calculator
Enter your sprinkler details. The tool estimates throw radius and planning values.
Example Data Table
These examples show how different settings affect estimated throw and runtime.
| Type | Nozzle | Pressure | Arc | Wind | Estimated radius | Spacing | Runtime (10 mm) |
|---|---|---|---|---|---|---|---|
| Rotary nozzle | 2.00 | 30 psi | 90° | Light | ~7.0 m | ~6.3 m | ~28 min |
| Fixed spray | 2.00 | 25 psi | 180° | Breezy | ~3.7 m | ~3.3 m | ~12 min |
| Impact | 3/16" | 3.0 bar | 360° | Calm | ~12.5 m | ~11.3 m | ~40 min |
Formula Used
The calculator starts with a typical base radius at a reference pressure. It then scales throw distance using a square-root pressure relationship and adjustment factors.
PressureFactor = √(P / Pref)
Radius = BaseRadius × PressureFactor × BrandFactor × InstallFactor × WindFactor
Area = π × Radius² × (Arc/360)
PrecipRate(mm/hr) = (Flow(L/hr) / Area(m²))
Spacing = Radius × SpacingFactor
Runtime(min) = (TargetDepth(mm) / PrecipRate(mm/hr)) × 60
These relationships match common irrigation planning approximations for throw and precipitation. Always verify against your sprinkler chart when precision matters.
How to Use This Calculator
- Select the sprinkler type closest to your installed head.
- Choose the nozzle size or setting that matches your nozzle.
- Enter operating pressure in psi, bar, or kPa.
- Enter flow rate for better precipitation and runtime estimates.
- Set arc, wind, and installation details to match your site.
- Click Calculate Radius to view results above the form.
- Use spacing and runtime to plan head layout and schedules.
- Download CSV or PDF to save and share calculations.
Sprinkler throw fundamentals for planning
Sprinkler radius is the estimated horizontal distance from the head to the outer edge of wet coverage. Manufacturers publish throw charts for each nozzle at specific pressures. This calculator provides a practical estimate by combining a typical base radius with pressure and site adjustments. Use it to compare scenarios quickly before final field verification.
Pressure, nozzle, and the square-root response
Throw distance typically increases as pressure rises, but it does not scale linearly. A common approximation is a square-root relationship: doubling pressure increases radius by about 41%. Nozzle size changes the starting point, because larger openings and rotor designs can sustain a longer stream at the same pressure. Keeping pressure stable across zones improves uniformity and reduces dry edges.
Arc settings and coverage area impacts
Arc does not usually change the maximum throw of a head; it changes the portion of the circle being watered. That is why the calculator reports an arc-adjusted area using π × r² × (arc/360). When you reduce the arc, the same flow is applied to a smaller area, raising the precipitation rate. Higher precipitation rates can require shorter runtimes to avoid runoff on slopes.
Wind, slope, and installation effects
Wind breaks up streams and deflects droplets, shortening effective radius and creating uneven patterns. Even light wind can reduce edge coverage, so spacing is often tightened below “head-to-head” placement. Tilted heads and sloped terrain can also distort the pattern, especially with fixed sprays. In the calculator, wind and installation factors apply conservative reductions to help avoid optimistic layouts.
Using results for spacing and runtime decisions
After you estimate radius, spacing is usually set between 75% and 100% of radius, depending on wind and desired overlap. The precipitation rate estimate converts flow into mm/hr by dividing liters per hour by the arc-adjusted area. With a target depth, runtime is calculated as (target ÷ precipitation) × 60 minutes. For accuracy, validate with a catch-cup test and adjust runtimes for soil intake and plant needs.
FAQs
1) Why does pressure increase not double the radius?
Throw often follows a square-root response, so gains slow as pressure rises. Increasing pressure may improve radius modestly while also increasing misting and drift on small sprays.
2) Should I use radius or diameter for head spacing?
Use radius for “head-to-head” spacing, where one head reaches the next. If the radius is 6 m, spacing near 6 m is typical, then reduce for wind or poor uniformity.
3) Does changing arc change the throw distance?
Arc usually changes coverage area, not the maximum throw. However, some heads behave differently at extreme arcs, so confirm with the product chart or a quick field test.
4) What flow rate should I enter if I only know zone flow?
Enter the flow for one head when estimating precipitation and runtime per head. If you only know total zone flow, divide it by the number of identical heads in that zone.
5) How do I choose a spacing factor?
Start at 0.90 for typical wind and real-world overlap. Use 0.95 to 1.00 in very calm, uniform conditions, or 0.80 to 0.90 for wind, slopes, or fixed sprays.
6) How accurate are these estimates compared to charts?
They are planning-level approximations using typical base radii and adjustment factors. For final designs, match your exact nozzle and pressure to the manufacturer chart and confirm uniformity with catch-cup testing.