The formula
Minutes per session = weekly inches ÷ application rate (in/hr) × 60 ÷ watering days
Example: 1 inch per week, 1.5 in/hr spray zone, 3 watering days: (1 ÷ 1.5) × 60 ÷ 3 ≈ 13 minutes per session. Compute yours in the Sprinkler Run Time Calculator.
Typical session times (1 inch weekly target, 3 days)
| Zone type | Application rate | Minutes per session |
|---|---|---|
| Fixed spray heads | 1.5-2 in/hr | 10-13 min |
| MP rotators | 0.5-0.9 in/hr | 22-40 min |
| Gear-drive rotors | 0.4-0.6 in/hr | 33-50 min |
| Drip (vegetables) | ~0.3-0.5 in/hr equivalent | 40-70 min |
Adjustments that matter
- Season: scale the weekly target with the weather - 1-1.5 in/week in peak summer for cool-season turf, near zero in spring/fall. Local reference ET data refines this.
- Soil: clay and slopes cannot absorb 13 minutes at once - split into cycle-and-soak (e.g. two 6-minute runs an hour apart).
- Rainfall: subtract effective rain from the target before scheduling.
From rate to schedule
Get your rate from head data with the Sprinkler Calculator (or a catch-cup test), then do the full plant-based version with the Irrigation Run Time Calculator, and set the weekly ceiling with the Water Budget Calculator.