Irrigation Runtime Calculator
Estimate irrigation water volume, total weekly runtime, runtime per zone and watering event, seasonal use and water cost.
Default project preview
17.3 minutes
Weekly water volume
2,494 gal
Total weekly runtime
208 min
Water per event
831 gal
Seasonal water use
64,831 gal
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Irrigated area
Enter this project assumption in ft². The current imperial default is 3000 ft².
Target weekly water depth
Enter this project assumption in in. The current imperial default is 1 in.
Application efficiency
Enter this project assumption in %. The current imperial default is 75 %. Minimum: 1. Maximum: 100.
Average active-zone flow
Enter this project assumption in gal/min. The current imperial default is 12 gal/min.
Equal-area zones
Enter this project assumption in a unitless value. The current imperial default is 4. Minimum: 1.
Watering days per week
Enter this project assumption in a unitless value. The current imperial default is 3. Minimum: 1. Maximum: 7.
Irrigation season
Enter this project assumption in weeks. The current imperial default is 26 weeks. Minimum: 1. Maximum: 52.
Water price
Enter this project assumption in per 1,000 gal. The current imperial default is 9 per 1,000 gal. Minimum: 0.
How to read the outputs
Weekly water volume
efficiency included. Default preview: 2,494 gal.
Total weekly runtime
all zones combined. Default preview: 208 min.
Water per event
all zones per watering day. Default preview: 831 gal.
Seasonal water use
26 weeks. Default preview: 64,831 gal.
Seasonal water cost
entered utility price. Default preview: $583.48.
Applied efficiency
distribution allowance. Default preview: 75%.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Weekly water volume = area × target depth ÷ application efficiency. Total runtime = weekly volume ÷ active-zone flow. Runtime per zone per event divides by equal zones and watering days.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use this calculator to translate a target irrigation depth into runtime using the zone precipitation rate and an editable efficiency factor. It helps schedule zones but does not account for soil infiltration, runoff or local watering restrictions by itself.
Calculation steps
- 1Choose the target water depth for the irrigation event.
- 2Enter the measured or manufacturer precipitation rate.
- 3Apply the efficiency factor.
- 4Divide target depth by effective rate and convert hours to minutes.
Worked numerical example
To apply 0.5 inch with sprinklers delivering 1.25 inches per hour at 80% efficiency, effective application is 1.0 inch per hour, so runtime is 30 minutes.
Purchasing and rounding
No purchasing quantity is generated. Use the result to program whole-minute controller runtimes and split long cycles when runoff begins.
Interpret the result
Long runtime can indicate a low precipitation rate, low efficiency or a high target depth. Runtime should be adjusted using soil moisture and observed runoff.
Page-specific assumptions
- Uniform zone precipitation.
- No rainfall credit unless entered separately.
- Pressure and nozzle performance remain stable.
- Efficiency reasonably represents overlap and wind loss.
Common mistakes
- Using flow rate instead of precipitation rate.
- Ignoring mixed nozzles in one zone.
- Applying the full runtime in one cycle on slow soil.
- Watering without seasonal adjustment.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Irrigation Runtime Calculator questions
Why divide by irrigation efficiency?+
Not all applied water reaches the root zone because of wind, evaporation, overspray and uneven distribution.
Should all zones use the same runtime?+
Only if zones have similar area, precipitation rate, plants, soil and exposure. Real systems often need different schedules.
What is cycle and soak?+
It splits a long runtime into shorter cycles so water can infiltrate instead of running off.