Sprinkler Run Time Calculator
Turn a catch-can test into your sprinkler precipitation rate and the run time to apply a target depth.
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What this tool does
The Sprinkler Run Time Calculator does the classic catch-can audit: average the water caught in tuna-can-style gauges during a timed run to get your system's real precipitation rate, then converts a target depth into run time, split into runoff-safe cycles.
How to use the Sprinkler Run Time Calculator
- Place identical straight-sided cans around the zone.
- Run the zone for the test minutes and measure the total ounces collected.
- Enter can diameter and count.
- Set your target depth (lawns typically want about 1 in per week, applied deeply).
- Program the cycles shown, with soak gaps between them.
Formula
Depth per can = (oz per can) ÷ (0.554 × can area in²); Rate (in/hr) = depth × 60 ÷ test minutes; Runtime = target ÷ rate × 60
- 0.554
- Fluid ounces in one cubic inch of water
Worked example
Six 4 in cans catching 24 oz total in 15 minutes: each can averaged 0.57 in, a rate of about 2.3 in/hr — too fast for most soils, so 1 in of water splits into 2 cycles.
Inputs
- Number of catch cans6
- Total water collected in all cans (fl oz)24
- Catch can diameter4 in
- Test run time (minutes)15
- Target water depth per watering1 in
- Max minutes per cycle (avoid runoff)20
Result
- Precipitation rate2.3 in/hr
- Total run time for target depth26 min
- Cycles needed2
- Minutes per cycle13.1 min
Results explained
- Precipitation rate
- Your system's measured output in inches per hour.
- Total run time
- Minutes to apply the target depth.
- Cycles
- Run time split at your max cycle length so water soaks in instead of running off (cycle-and-soak).
Frequently asked questions
It depends entirely on your precipitation rate: run time = target depth ÷ rate. A system putting out 0.5 in/hr needs 2 hours for 1 in of water; a rotor zone at 0.25 in/hr needs 4.
Scatter 4–6 identical straight-sided cans (tuna cans work) across the zone, run it 15 minutes, and measure each can's depth or volume. This tool converts total ounces and can diameter into the rate.
Spray heads often deliver 1–2.5 in/hr (faster than most soils absorb — use cycle-and-soak), rotors 0.25–0.6 in/hr, and drip is measured differently. Matching run time to your measured rate is what matters.
When the application rate beats the soil's intake rate, water runs off. Cycling (e.g. 2 × 15 min with an hour between) lets each dose soak in — same total depth, far less waste.
About 1 in per week including rainfall is the standard guidance for most turf in summer, applied in 1–2 deep waterings rather than daily sprinkles.