Sprinkler Zone Calculator
How many heads per zone from available GPM and head flow.
Enter your values
Enter the available flow in GPM.
Enter the flow per head in GPM.
Enter the total heads needed you are working with.
Enter the water needed per week in in.
Enter the precipitation rate in in/hr.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Heads per zone
- 4
- Zones required
- 6
- Zone flow
- 7.2 GPM
- Weekly run time per zone
- 150 minutes
- Split into 3 days
- 50 minutes per session
Working
- 10.75 x 10 GPM / 1.8 = 4 heads per zone
Quick answer
Heads per zone = usable flow (about 75% of available GPM) divided by the flow of one head. Zones = total heads divided by heads per zone.
heads per zone = 0.75 x GPM / GPM per head
At a glance
| What it does | How many heads per zone from available GPM and head flow. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Available flow, Flow per head, Total heads needed, Water needed per week, Precipitation rate |
| Main output | Heads per zone |
| Formula | heads per zone = 0.75 x GPM / GPM per head |
| Cost | Free — no sign-up, no download |
How to use the Sprinkler Zone Calculator
- 1Measure available flow by timing how long a 5 gallon bucket takes to fill from an outside tap.
- 2Get GPM per head from the nozzle chart at your operating pressure.
- 3Keep 25% headroom so pressure stays high enough for even coverage.
Inputs explained
- Available flow(GPM)
- Enter the available flow in GPM.
- Flow per head(GPM)
- Enter the flow per head in GPM.
- Total heads needed
- Enter the total heads needed you are working with.
- Water needed per week(in)
- Enter the water needed per week in in.
- Precipitation rate(in/hr)
- Enter the precipitation rate in in/hr.
Worked example
Using the values the calculator loads with:
Inputs
- Available flow10 GPM
- Flow per head1.8 GPM
- Total heads needed24
- Water needed per week1 in
- Precipitation rate0.4 in/hr
Results
- Heads per zone4
- Zones required6
- Zone flow7.2 GPM
- Weekly run time per zone150 minutes
- Split into 3 days50 minutes per session
- 0.75 x 10 GPM / 1.8 = 4 heads per zone
Frequently asked questions
Why not run every head at once?
Flow is shared. Too many heads on one zone drops pressure, the spray falls short and you get dry rings between heads.
How long should each zone run?
Long enough to apply about 1 inch of water per week, split across 2 to 3 sessions so it soaks in instead of running off.
What do I need to enter into the Sprinkler Zone Calculator?
Just 5 values: available flow, flow per head, total heads needed, water needed per week, precipitation rate. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Sprinkler Zone Calculator work out the answer?
Heads per zone = usable flow (about 75% of available GPM) divided by the flow of one head. Zones = total heads divided by heads per zone. It applies the formula heads per zone = 0.75 x GPM / GPM per head and shows the working so you can check each step by hand.
Is the Sprinkler Zone Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.