Sprinkler Coverage Calculator
Calculate how many sprinklers you need for your lawn.
Select sprinkler type and enter lawn area for spacing and quantity recommendations.
Sprinkler coverage and water usage calculations ensure your lawn gets the right amount of water without waste, overrun, or dry spots. Efficient irrigation design also reduces your water bill significantly.
Coverage area by head type:
Coverage Area = π × Radius² × (Arc / 360°)
For a full-circle head (360°): Area = π × R² For a half-circle head (180°): Area = π × R² × 0.5
Water output calculation:
Flow Rate (GPM) = Pressure (PSI) × Orifice Factor
Application Rate (in/hr) = (GPM × 96.25) / Coverage Area (sq ft)
Worked example: A rotary head with 15-ft radius, 180° arc, flow rate 2.0 GPM:
- Coverage: π × 15² × 0.5 = 353 sq ft
- Application rate: (2.0 × 96.25) / 353 = 0.55 inches/hour
- To apply 1 inch of water: run time = 1.0 / 0.55 = 1.8 hours
Recommended weekly water amounts by grass type:
| Grass Type | Weekly Need |
|---|---|
| Kentucky Bluegrass | 1.0–1.5 inches |
| Bermuda | 0.75–1.25 inches |
| Zoysia | 0.75–1.0 inches |
| Fescue | 1.0–1.5 inches |
| St. Augustine | 1.0–1.5 inches |
Precipitation rate matching: When zoning a system, all heads in one zone should have matching precipitation rates. Mixing pop-up spray heads (1.5–2.5 in/hr) with rotor heads (0.4–0.8 in/hr) in the same zone causes severe over/under watering.
Best watering time: Early morning (4–8 AM) reduces evaporation by up to 30% compared to midday watering and prevents fungal growth that occurs when foliage stays wet overnight.