Irrigation PR & Runtime Calculator

Calculate precipitation rates, distribution uniformity, and optimal zone runtimes.

System Inputs

Efficiency & Runtime

Comma-separated values to calculate DU(lq). Leave blank for 100% uniformity.
Used for cycle and soak splitting to prevent runoff.

Results

Precipitation Rate (PR)
0.00 in/hr
Constant used: 96.3
Distribution Uniformity (DU_lq)
100 %
Assumed ideal uniformity.
Total Recommended Runtime
0 min
To achieve target depth adjusted for uniformity.
Cycle & Soak Plan
-

About the Irrigation Precipitation Rate & Runtime Calculator

An irrigation precipitation rate calculator helps landscape architects, agronomists, and turf managers design highly efficient watering schedules. By determining the exact inches per hour delivered by your sprinklers, you can match infiltration rates to soil types, preventing costly water runoff and promoting significantly deeper root growth.

How it works

  1. Enter the total flow rate in gallons per minute for the specific irrigation zone.
  2. Input the total square footage covered by those sprinkler heads.
  3. Apply the standard formula to find the precipitation rate and calculate the exact runtime needed.

Frequently asked questions

What is the formula for calculating precipitation rate?

The standard formula is Precipitation Rate = (96.3 x Total GPM) / Total Area. The 96.3 is a constant that converts gallons per minute into inches per square foot per hour.

Why is distribution uniformity (DU) important?

DU measures how evenly water is applied across the zone. A low DU means some areas stay dry while others are overwatered, requiring longer runtimes to fix the dry spots.

How does soil type affect irrigation runtimes?

Heavy clay soils have low infiltration rates. To prevent runoff, irrigation must be applied in short bursts using a cycle-and-soak method rather than one long continuous runtime.

Should I mix different types of sprinkler heads in one zone?

No. Rotors, spray heads, and drip lines have vastly different precipitation rates. Mixing them makes it impossible to apply water uniformly across the landscape.

References