Zone Fill Time Calculator

1) Required volume

• Convert area to sqft and depth to inches.
• Cubic feet = Area(sqft) × Depth(in) ÷ 12
• Gallons = Cubic feet × 7.48051948
• Adjusted gallons = Gallons × (1 + Allowance% ÷ 100)

2) Effective flow

• Total flow comes from either a direct reading, or emitters.
• Effective flow = Total flow × Efficiency factor

3) Fill time:

Fill time (minutes) = Adjusted gallons ÷ Effective flow (gpm)

1. Enter your zone area and choose the correct unit.
2. Enter your target water depth for the irrigation cycle.
3. Select Total Flow Rate or Emitters.
4. Set an efficiency factor to reflect real delivery conditions.
5. Optionally add an allowance percentage for practical buffers.
6. Press Calculate to view results above the form.
7. Export CSV or PDF after the first saved calculation.

Target depth is the most practical way to describe a zone “fill.” A 0.5 in cycle on 1,000 sqft applies about 311 gallons before any allowance. Converting depth to inches and area to square feet keeps the math consistent across units. For gardens, shallow frequent cycles often reduce runoff on compacted soils. For beds with mulch, a deeper cycle may be better, but watch infiltration limits.

Total flow can come from a meter reading or from emitters. If a header delivers 8 gpm, that equals about 30.3 L/min, but clogged screens or pressure drops can lower it. For drip, multiply emitter count by emitter rating (gph or L/h) to get a zone total. Use a bucket test on one outlet to validate the label rate in conditions. Record pressure at the valve.

Efficiency factor represents how much of the measured flow becomes useful water in the target area. A value of 0.85 is common when leaks, wind drift, and uneven distribution exist. If a zone has overspray or steep slopes, reduce efficiency or add an allowance percentage to protect plant needs. The calculator applies allowance to required volume first, then multiplies flow by efficiency to compute effective flow.

Fill time is returned in minutes and hh:mm:ss, which helps when controllers accept different formats. After you get a runtime, split long cycles into two starts to improve soak-in, especially on clay. For example, 40 minutes could become two 20-minute runs with a pause. When water is limited, compare zones by gallons per cycle to prioritize high-value beds and new plantings. Demand rises during hot spells.

Use field observations to refine inputs over time. Place catch cups or tuna cans across the zone and run a short test to see how evenly water lands. If outer areas stay dry, your effective efficiency is lower than expected. Clean filters, check for broken heads, and confirm nozzle sizes match the design. Recalculate after upgrades, and export CSV or PDF to keep a seasonal log.

1) What does zone fill time represent?

Zone fill time is the runtime needed to apply a chosen water depth over a zone, after adjusting for allowance and delivery efficiency. It helps translate volume targets into controller minutes.

2) How do I pick a target depth?

Use shallow depths for frequent cycles on tight soils, and deeper depths for established beds with good infiltration. Start with 0.25–0.75 in, then adjust using plant response and soil moisture checks.

3) What efficiency factor should I use?

Use 0.95–1.00 for well-tuned drip and low-wind micro-sprays. Use 0.75–0.90 for mixed coverage, overspray, or older heads. Lower values increase runtime because effective flow is reduced.

4) Can I enter metric units?

Yes. Area can be m² and depth can be mm or cm. Flow can be L/min, and emitter rates can be L/h. The calculator converts everything internally for consistent results.

5) How can I estimate total flow without a meter?

Use emitter totals for drip, or run a bucket test at a representative outlet. Measure the time to fill a known volume and convert to flow rate, then apply an efficiency factor.

6) Why add an allowance percentage?

Allowance adds a buffer for runoff risk, wind drift, uneven distribution, or scheduling gaps. It increases required volume before runtime is computed, producing a more conservative fill time.