SettingsSettings for this calculationUS
Your water supply's available flow rate, in the unit shown.
Measure by timing how long it takes to fill a bucket of known size (say 20 L or 5 gallons) from an outdoor spigot at full flow, then divide that volume by the time in minutes. Leave some margin below your absolute maximum for household use during irrigation.
The rated flow rate of the sprinkler head you're using.
Check the manufacturer's spec sheet — spray heads, rotors, and drip emitters all have very different flow rates.
Maximum heads per zone
5 heads per zone
This is a flow-based estimate only — also check that your zone valve and pipe sizing can handle the combined flow, and that static water pressure is sufficient for the specific heads chosen.
They open the calculator with your figures already in it
Irrigation Zone Calculator: 5 heads per zone — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Maximum heads per zone = available water flow ÷ flow rate per sprinkler head (both in the same flow unit)
Inputs used
- Available Water Flow
- 10 gal/min
- Flow Rate per Sprinkler Head
- 2 gal/min
Confidence note: This is a flow-based estimate only — also check that your zone valve and pipe sizing can handle the combined flow, and that static water pressure is sufficient for the specific heads chosen.
What this calculation does not cover
- One flow rate is divided into the supply, so the count only holds for a zone whose heads all pass the same amount; a run that mixes rotors with sprays, or two nozzle sizes on the same valve, has no single divisor and has to be added up head by head instead.
- Nothing here looks at the ground — this is a ceiling set by the water supply, not a head count for the area being watered, and a lawn needing more heads than this figure allows is a lawn that has to be split across further zones.
- The remainder is dropped rather than reported: the division is floored to whole heads, and the leftover flow, which can be almost a full head's worth, is not shown, so the answer gives no sense of how much spare capacity the zone is left running on.
- The smallest head flow the box accepts is 0.1 L/min (0.03 gal/min), which is well above what a single drip emitter passes even though the input's own note points at drip — a drip zone has to be entered as the flow of a whole lateral, not one emitter.
- There is no time anywhere in the arithmetic. It answers how many heads can run at once, not how long the valve must stay open, so it settles nothing about the depth of water the planting actually receives.
Add the equipment this sizes
This result is a specification — 5 heads per zone — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Part of a bigger job
This trade is one line of a job takeoff. Run the whole job and every other trade comes back with it, off the same measurements.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-05 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Maximum heads per zone = available water flow ÷ flow rate per sprinkler head (both in the same flow unit)
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