BYTETOOLS

Sprinkler Run Time Calculator

Work out sprinkler precipitation rate from head spacing and flow, then get run minutes per zone with a cycle-and-soak schedule matched to your soil and slope.

1.28
Precipitation rate (in/hr)
0.90
Adjusted rate (in/hr)
66.8
Run time per week (min)
22.3
Run time per day (min)

Cycle and soak

4
Cycles per watering day
5.6
Minutes per cycle
5.8
Max minutes before runoff
30
Soak between cycles (min)
StepActionMinutesWater applied (in)
1Run zone, then soak 30 min5.60.083
2Run zone, then soak 30 min5.60.083
3Run zone, then soak 30 min5.60.083
4Run zone5.60.083

The heads put down 1.28 in/hr but the soil and slope only take about 0.25 in/hr. Split the run into 4 cycles of about 5.6 minutes with a soak in between, or water runs off the lawn and down the drive.

12.0
Zone flow (GPM)
20%
Spare service flow
801
Water per week (gal)

Precipitation rate = 96.3 × GPM ÷ (head spacing × row spacing), where 96.3 comes from 231 in³ per gallon × 60 minutes ÷ 144 in² per square foot. A 3 GPM rotor on 30 × 30 ft spacing works out at 0.32 in/hr, which is why rotors run so much longer than sprays. Triangular spacing uses 0.866 × the row spacing. Run time = weekly requirement ÷ rate, divided by the number of watering days, then split into cycles short enough for your soil to absorb. Catch-cup testing beats every calculation here — this is a starting point, not a substitute. Estimates only.

What is the Sprinkler Run Time Calculator?

The ByteTools Sprinkler Run Time Calculator starts with the industry formula: precipitation rate = 96.

  • Precipitation rate from square, triangular or whole-zone layouts, or from catch-cup data
  • Distribution-uniformity adjustment so the driest quarter still gets watered
  • Cycle-and-soak schedule built from soil intake rate, slope and surface storage
  • Step-by-step cycle table showing minutes and water applied per pass
  • Zone GPM against available service flow, with an over-draw warning
  • Copyable schedule; every calculation runs locally in your browser

How to use the Sprinkler Run Time Calculator

  1. 1

    Choose whether the precipitation rate comes from head spacing or from a catch-cup test you have already done.

  2. 2

    Enter the zone flow in GPM, the number of heads, and the head and row spacing — or the zone area for a whole-zone calculation.

  3. 3

    Set the weekly water requirement in inches, how many days a week you water, and the distribution uniformity of your heads.

  4. 4

    Pick your soil type and slope, and set the surface storage and soak time, to get a cycle-and-soak schedule.

  5. 5

    Check the service-flow figure to make sure the zone is not drawing more than the supply can deliver, then copy the schedule.

About the Sprinkler Run Time Calculator

The ByteTools Sprinkler Run Time Calculator starts with the industry formula: precipitation rate = 96.3 × GPM ÷ (head spacing × row spacing). A 3 GPM rotor on 30 by 30 foot spacing puts down 0.32 inches an hour, which is why rotors run so much longer than fixed sprays. You can also enter a rate you measured with catch cups.

Run time is then the weekly water requirement divided by that rate, adjusted for distribution uniformity so the dry quarter of the zone still gets what it needs, and split across your watering days. If the heads apply water faster than the soil takes it, the calculator works out how many cycles it takes before runoff starts and builds a cycle-and-soak schedule.

A service-flow check flags zones that draw more than the supply can deliver. Everything is computed in your browser, with nothing uploaded. Catch-cup testing beats every calculation here — treat this as a starting point rather than a substitute.

Frequently asked questions

How long should I run my sprinklers?

Divide the weekly water requirement by your precipitation rate. At 1 inch a week and a rate of 1.7 in/hr you need about 35 minutes a week, or roughly 12 minutes on each of three watering days — but rotors at 0.32 in/hr need well over three hours a week.

What is a sprinkler precipitation rate?

It is how many inches per hour the heads apply, calculated as 96.3 × GPM ÷ (head spacing × row spacing). The 96.3 comes from 231 cubic inches per gallon × 60 minutes ÷ 144 square inches per square foot. Fixed sprays run 1.5 to 2 in/hr; rotors are usually 0.3 to 0.5.

What is cycle and soak watering?

Instead of one long run, you split the time into shorter cycles with a soak between them so the water has time to move into the soil. It is the fix for clay soils and slopes, where the heads apply water far faster than the ground can absorb it and the surplus runs off.

How much water does a lawn need per week?

Cool-season turf in summer typically wants 1 to 1.5 inches a week including rainfall, delivered in two or three deep soakings rather than daily sprinkles. Warm-season grasses generally need less. Local extension services publish figures for your climate and grass type.

What is distribution uniformity and why does it matter?

It measures how evenly the heads apply water across the zone. At 70% uniformity the driest quarter gets only 70% of the average, so you have to run longer to keep those spots alive — which means over-watering everywhere else. Improving uniformity saves more water than trimming minutes.

How do I test my sprinkler precipitation rate with catch cups?

Set several straight-sided containers across the zone, run it for a set time, then measure the depth in each. Average depth divided by test minutes times 60 gives inches per hour, and the spread between the cups gives you the distribution uniformity. Enter that measured rate here.

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