Use these numbers to test the calculator quickly.
| Scenario | Zone | Area | Precip | Depth | Efficiency | Days/week |
|---|---|---|---|---|---|---|
| Mixed beds | Front beds | 50 m² | 25 mm/hr | 10 mm | 70% | 3 |
| Side beds | 35 m² | 20 mm/hr | 10 mm | 70% | ||
| New planting | Shrubs | 40 m² | 18 mm/hr | 15 mm | 65% | 4 |
| Lawn strip | 60 m² | 30 mm/hr | 12 mm | 75% |
- Run time (minutes):
(Depth ÷ PrecipRate) × 60 ÷ Efficiency - Volume per event:
Area × Depth ÷ Efficiency(metric uses liters where 1 mm·m² = 1 L) - Required flow:
Volume ÷ RunTime - Cycle-soak time:
RunTime + (Cycles−1) × SoakMinutes - Monthly estimate:
WeeklyVolume × (30 ÷ 7)
- Choose Metric or Imperial units.
- Enter each zone’s area, rate, depth, and efficiency.
- Set days per week for weekly and monthly estimates.
- Enable cycle-soak to reduce runoff on tight soils.
- Enter available flow to validate your chosen mode.
- Press Calculate to view results above the form.
- Download CSV or PDF for documentation.
Two-zone irrigation planning for consistent results
A two-zone layout is a practical way to match water delivery to plant needs. This calculator converts your zone area, precipitation rate, and target depth into runtime, flow demand, and water-use estimates, then highlights whether your selected run mode fits the flow you have available. For most gardens, separating turf from beds improves uniformity and reduces wasted water.
1) Translate depth goals into runtime
Depth per event is the “how much” of irrigation you want in a single session. Example: applying 10 mm at 25 mm/hr needs about 24 minutes at 100% efficiency. With a realistic 70% efficiency, runtime increases to roughly 34 minutes. This adjustment helps you plan for wind, overspray, and distribution losses.
2) Understand precipitation rate differences
Spray heads often deliver higher rates than rotators and drip systems. A zone at 20 mm/hr will need longer runtime than a zone at 30 mm/hr for the same depth. Use nozzle charts or an irrigation audit to enter a reliable rate. Even a 10% rate error can noticeably change runtime and monthly totals.
3) Use cycle-soak to reduce runoff
On compacted or clay soils, longer continuous runs can exceed infiltration and cause runoff. Cycle-soak splits runtime into multiple short cycles with soak breaks. If your total runtime is 36 minutes and the max cycle is 12 minutes, you’ll run three cycles. Adding a 20-minute soak between cycles increases schedule time, but improves absorption.
4) Validate flow for sequential or simultaneous runs
Required flow is calculated from event volume divided by runtime. When zones run simultaneously, the combined flow is the sum of both zones. When zones run sequentially, the limiting case is the larger of the two. If available flow is tight, choose sequential mode or reduce nozzle demand.
5) Estimate weekly and monthly water use
The calculator reports weekly volume using your selected days per week and estimates a 30-day month. For planning, set days per week to match your typical schedule and compare scenarios. Example totals help justify upgrades: improving efficiency from 65% to 75% can reduce volume for the same soil depth and often shortens runtime. Track these outputs and adjust seasonally.
Frequently asked questions
1) What is a “two-zone” setup?
It means the garden is divided into two irrigation zones with independent runtimes. Each zone can match a different area, precipitation rate, and plant demand. This improves uniformity and makes scheduling easier.
2) How do I find precipitation rate for a zone?
Use the nozzle manufacturer’s chart for your head/nozzle model and spacing, or perform a catch-cup test to measure applied depth per hour. Enter that value as the precipitation rate.
3) What efficiency percentage should I use?
Many residential systems land around 60–80% depending on wind exposure, overspray, and nozzle quality. If you have measured distribution uniformity, use that figure. Otherwise start at 70% and refine after observations.
4) When should I enable cycle-soak?
Turn it on when you see runoff, puddling, or water moving off the irrigated area. Cycle-soak is especially helpful for clay soils, slopes, and compacted lawns. It improves infiltration without changing your total applied depth.
5) What does “available flow” represent?
It is the usable flow at the zone manifold or valve, after pressure regulation and losses. If you know your supply flow from a bucket test or meter, enter it to check whether your chosen run mode is feasible.
6) Why does simultaneous mode need more flow?
When both zones run at once, the system must supply the sum of each zone’s required flow. If that combined demand exceeds available flow, pressure drops and coverage can degrade. Sequential mode avoids this by running one zone at a time.
7) How accurate are monthly cost estimates?
They are planning estimates based on your entered days per week and a 30-day month. Weather, restrictions, and seasonal adjustments will change real use. For better accuracy, update depth and frequency monthly and compare exports over time.