Irrigation Zone Calculator

1. Enter coverage area. Measure the total area in square feet that needs irrigation coverage.

2. Select head type. Spray heads cover smaller areas (10-15 ft radius) and are best for lawns and flower beds. Rotors cover larger areas (25-40 ft radius) for open lawns. Drip is for beds and plantings.

3. Set GPM per head. Check your head manufacturer's specs. Typical spray heads run 1-3 GPM, rotors 3-15 GPM, and drip emitters 0.5-2 GPM.

4. Set zone GPM limit. This depends on your water supply flow rate. Most residential meters supply 15-25 GPM. Do not exceed your water supply capacity.

The calculator uses head-to-head spacing coverage calculations and GPM zone splitting:

Head-to-head spacing means placing heads so that each head's spray reaches the next head. This ensures uniform coverage with no dry spots. The precipitation rate tells you how many inches of water per hour the system applies. Target 0.5-1.5 inches per hour for optimal absorption without runoff.

Designing new irrigation systems. Calculate head count, zone layout, and controller size before ordering materials. Getting the zone count right prevents undersized valves and pressure problems.

Bidding irrigation jobs. Accurate head counts mean accurate material estimates. No more guessing on pipe, fittings, and wire quantities.

Troubleshooting existing systems. Check if the precipitation rate is in the target range. Uneven watering often means the system was designed with the wrong head spacing or too many heads per zone.