Calculator
Sprinkler Zone Calculator
Work out how many irrigation zones your available water flow supports.
Verified August 2026
Zones required
4
2 heads per zone
- Total heads
- 7
- Usable design flow
- 7.5 GPM
- Flow per zone
- 6 GPM
- Runtime for 1 in of water
- 2.3 hours (all zones)
Estimates only. Local pricing, site conditions and code requirements change the real number.
The formula
Heads per zone = available GPM / GPM per head; Zones = total heads / heads per zone
Never design a zone above 75% of available flow. Rotors and spray heads must never share a zone — their precipitation rates are completely different.
Worked example
A 10 GPM supply with 3 GPM rotors supports 2 heads per zone, so a 6,000 sq ft lawn needs about 6 zones.
Frequently asked questions
How many sprinkler heads per zone?
Divide 75% of your available GPM by the flow of one head. With 10 GPM available and 3 GPM rotors, that is two heads per zone.
How do I find my available GPM?
Time how long a 5-gallon bucket takes to fill from an outdoor spigot. 30 seconds means 10 GPM.
Sources
Sources & verification
Last verified August 2026. Cost figures are modeled estimates based on national baselines adjusted for local labor and material pricing — they are not quotes. Permit rules change; confirm with the building department before starting work.