GARDEN FIELD BOOK / CALCULATOR 12
Sprinkler Run Time Calculator
Measure how deeply your sprinkler waters in a timed catch-cup test. Enter the depth in each cup or a measured application rate, then use your own target depth to calculate sprinkler minutes. See coverage variation before trusting one average.
0.25 in average catch in 15 minutes
Measured rate: 1.00 in/hr. Entered target: 0.50 in. Required total run: 30 minutes.
YOUR SPRINKLER MEASUREMENTS
Enter the catch-cup test
CALCULATED OUTPUT
Your sprinkler run time
Enter catch-cup readings and a target depth to see an estimated run time, application rate and coverage spread.
These are runtime portions only. Rest periods must be chosen from observed runoff and infiltration, not guessed here.
This is an arithmetic estimate from your measurements, not a recommendation for irrigation depth or frequency. Watering may vary across the zone; check local restrictions and stop if runoff begins.
FROM CUPS TO MINUTES
How to measure application depth
Spread identical cups across the zone
Use level, straight-sided catch containers that measure water depth. Include edges, middle and low-coverage areas, not just the wettest spots. A quick calculator estimate is not a full irrigation audit.
Time one complete sprinkler test
Run the same zone for a measured number of minutes. Read each cup in inches or millimeters. An empty cup should be entered as zero rather than omitted.
Supply your own target depth
Set the application depth from local guidance and growing conditions. This calculator changes a depth target into a time; it does not choose the target for you.
CALCULATION METHOD
Turn average catch depth into sprinkler minutes
Worked example: four cups collect 0.20, 0.30, 0.25 and 0.25 inches during 15 minutes. Their average is 0.25 in, the measured rate is 1.00 in/hr, and a separately chosen target of 0.50 in requires 30 minutes at that rate. The same calculation works in millimeters when both measured and target depths use millimeters.
A manual measured-rate input skips the cup-average step. Do not substitute sprinkler GPM for precipitation depth per hour: water flow and application depth are different measurements.
WHAT THE AVERAGE CANNOT GUARANTEE
Check uneven coverage before changing the timer
One average can hide dry spots
Dry and wet cups may differ sharply, especially near edges or weak sprinkler overlap. More minutes do not automatically correct an uneven pattern. Check actual sprinkler alignment and coverage first.
Split time only when needed
The optional maximum cycle length divides calculated minutes into smaller runtime portions. It does not estimate soak time or soil infiltration. Stop or pause if water starts running off.
A target is not a universal recommendation
Watering depth and frequency depend on local conditions, soil, weather, root zone and site use. Enter an appropriate target from guidance relevant to your location; do not treat the example as an instruction.
CONTINUE WITH GARDEN FIELD BOOK
Apply your measurements in the right context
Find more tools in the Garden Calculators & Planning Tools directory.