Sprinkler Run Time Calculator: Minutes per Watering

This calculator turns a weekly watering target into minutes of sprinkler run time. Enter the inches of water you want per week, the precipitation rate of the zone in inches per hour, and the number of waterings per week; you get the minutes per watering and per week.

Formula

Weekly run time (minutes) = water per week (in) ÷ precipitation rate (in/h) × 60. Run time per watering = weekly run time ÷ number of waterings.

• tgt: inches of water to apply each week (rain counts toward it)
• pr: how many inches per hour the zone applies; measure it with catch cups or use the precipitation rate calculator
• n: number of watering days per week

Worked Example

1 in per week, a spray zone at 1.5 in/h, three waterings.

1. Weekly = 1 ÷ 1.5 × 60 = 40 minutes, shown as 40:00
2. Per watering = 40 ÷ 3 = 13.33 minutes, shown as 13:20

How to use the result

Set each zone’s timer separately, because spray heads and rotors apply water at very different rates. If water runs off before the time is up, split the run into two shorter cycles with a soak break between them.

Limits and common mistakes

• Subtract rain from the weekly target; a rain gauge tells you how much fell.
• Local watering rules may limit days or times; follow them.
• Shade, slopes and soil type change what a lawn needs; adjust from what you see.

Frequently Asked Questions

How long should I run sprinklers to apply 1 inch?

At 1.5 in/h, 40 minutes; at 0.5 in/h (typical rotors), 2 hours.

How do I find my precipitation rate?

Set out straight-sided cups, run the zone 15 minutes, measure the average depth and multiply by 4.

Is it better to water more often for less time?

Fewer, deeper waterings usually encourage deeper roots; follow local advice.

Does the time format mean hours?

Results read minutes:seconds under an hour and h:mm:ss above.

in tgt | Water per week | in | 1 | 0 | 5
in pr | Precipitation rate of the zone | in/h | 1.5 | 0.01 | 10
in n | Waterings per week | times | 3 | 1 | 14
out ses | Run time per watering | h:mm:ss | tgt / pr * 60 / n | time
out wk | Run time per week | h:mm:ss | tgt / pr * 60 | time