| Scenario | Area | Target depth | Rate method | Rate | Efficiency | Estimated runtime |
|---|---|---|---|---|---|---|
| Lawn zone, rotary heads | 800 sq ft | 0.60 in | Known rate | 0.70 in/hr | 80% | ~64 minutes |
| Garden bed, drip emitters | 250 sq ft | 0.40 in | Emitters | 120 emitters x 1 gph | 90% | ~21 minutes |
| Vegetable plot, spray stakes | 40 m2 | 15 mm | Known rate | 20 mm/hr | 85% | ~53 minutes |
| Orchard row, drip | 60 m2 | 10 mm | Emitters | 50 emitters x 8 L/hr | 90% | ~13 minutes |
- Runtime basis depth = Target depth divided by (Efficiency divided by 100).
- Total runtime (hours) = Runtime basis depth divided by Application rate.
- Total runtime (minutes) = Total runtime (hours) multiplied by 60.
- Drip rate (Imperial) = Total flow (gph) divided by (0.623 multiplied by Area in sq ft).
- Drip rate (Metric) = Total flow (L/hr) divided by Area in m2.
- Volume (Imperial) = Area (sq ft) multiplied by Depth (in) multiplied by 0.623 gallons.
- Volume (Metric) = Area (m2) multiplied by Depth (mm) equals liters.
- Select a unit system that matches your measurements.
- Enter the irrigated area of one zone.
- Choose a target depth based on your soil and plants.
- Pick a method: enter a known rate or use emitter flow.
- Set efficiency to reflect wind, slope, and uniformity.
- Increase cycles when runoff or puddling occurs.
- Press calculate to see runtime above this form.
- Download CSV or PDF if you need a record.
Zone Measurement and Scheduling Inputs
Accurate runtime starts with measuring one irrigation zone at a time. Use the wetted footprint of sprinklers or the planted bed outline for drip. Enter the area and choose a target depth that matches root depth, soil texture, and season. A deeper target supports fewer watering days, while a shallower target supports frequent refresh cycles.
Understanding Application Rate and Uniformity
Application rate is the depth delivered per hour. For sprinklers, the most reliable rate comes from a catch-can test placed across the zone. For drip, the rate is derived from total emitter flow spread over the zone area. Uniformity matters: overlapping patterns and pressure variation can cause dry spots even when the average rate looks correct.
Efficiency and Loss Adjustments
Efficiency represents real-world losses from wind drift, evaporation, runoff, and non-uniform coverage. The calculator increases runtime to deliver the intended soil depth after accounting for these losses. Use higher efficiency for calm conditions and well-tuned systems, and lower efficiency for windy sites, steep slopes, or older sprinklers.
Cycle and Soak Strategy for Infiltration
When water ponds or runs off, split the total runtime into multiple cycles. Shorter cycles allow water to infiltrate between runs, reducing waste and improving root-zone storage. This approach is especially effective on clay soils and compacted lawns. Adjust cycle count until the surface remains stable during irrigation.
Interpreting Volume Outputs for Management
Volume outputs help you estimate consumption and plan irrigation budgets. In imperial units, gallons are derived from inches over square feet. In metric units, liters align with millimeters over square meters. Compare target versus applied volume to understand how efficiency drives real water use and to fine-tune schedules over time.
- Imperial: Area 600 sq ft, target depth 0.50 in, rate 0.80 in/hr, efficiency 85%, cycles 2.
- Metric: Area 45 m2, target depth 12 mm, rate 18 mm/hr, efficiency 90%, cycles 3.
1) How do I find my sprinkler application rate?
Run the zone for 15 minutes, measure collected water in several cups, average the depth, then convert to an hourly rate by multiplying by four. Use multiple locations to reflect coverage variation.
2) What target depth should I choose?
Use deeper targets for established turf and shrubs, and moderate targets for beds. Sandy soils often need smaller depths more frequently, while loamy soils can store more water per cycle.
3) Why does efficiency change the runtime?
Efficiency accounts for water that does not reach the root zone. Lower efficiency means more runtime is required to deliver the same soil depth, which increases applied volume and total watering time.
4) When should I use multiple cycles?
Use multiple cycles if you see runoff, puddling, or water moving off the zone. Splitting runtime improves infiltration and reduces waste, especially on slopes, clay soils, and compacted areas.
5) Can I use emitter flow to estimate a drip runtime?
Yes. Enter emitter count and flow per emitter to estimate an equivalent depth rate across the zone area. This is useful when you do not have a measured depth rate from field testing.
6) Why do drip and sprinkler results differ for the same depth?
They distribute water differently. Sprinklers cover the surface area evenly, while drip concentrates water near plants. The same target depth can require different runtimes depending on flow, spacing, and wetted area.
7) How should I adjust the schedule through the season?
Keep the depth logic, then change frequency as conditions shift. Hot, windy periods may need more frequent watering, while cooler weeks may need less. Re-test rates after maintenance or nozzle changes.
- Measure rate with catch-cans for the most reliable runtime.
- Use shorter cycles on clay soils and slopes.
- Adjust seasonally as temperature and wind change.