Irrigation Calculator

It depends on your sprinkler head type and how much water you want to deliver in a week. This calculator runs the actual formula: your target weekly watering depth divided by your head type's application rate gives total weekly run time, then splits that across however many sessions a week you water. Spray heads apply water roughly three to four times faster than rotor heads, so the same target depth needs a very different run time depending which type is installed.

Enter your zone's area, head type and target weekly watering depth above for an exact figure; there is no single minute count that applies everywhere, since it depends on application rate. As a general shape, a spray-head zone delivering a common 1 to 1.5 inch weekly target often lands in the 30 to 60 minute range for the whole week's watering, while a slower rotor-head zone needs roughly three to four times as long to deliver the same depth.

Colorado State University Extension's "Sprinkler Types Used for Lawn Irrigation" gives spray heads at roughly 1 to 2.5 inches per hour and rotor heads at roughly 0.25 to 0.75 inches per hour. The difference comes from how each head works: a spray head wets its whole pattern at once, while a rotor head sweeps a single stream across the same area, applying water much more slowly.

A spray head sprays a fixed fan pattern continuously the moment it pops up. A rotor head rotates a single stream back and forth across its coverage area instead of spraying it all at once, which is why rotor heads apply water three to four times slower than spray heads, per Colorado State University Extension. Mixing the two head types on one zone with one run time is a common design mistake, since they need very different run times to deliver the same depth of water.

It depends on the area covered and the target watering depth: gallons equal area in square feet times depth in inches divided by 12, times 7.48 gallons per cubic foot. This calculator runs that conversion for you once you enter your zone's area and target, in addition to the run time needed to deliver it.

University of Missouri Extension's MG10 publication states Transition Zone lawns may need up to 1 to 1.5 inches of water weekly from rainfall and irrigation combined, which this calculator uses as an editable starting default. Actual need shifts with grass type and climate; the Lawn Watering Calculator works out a target specific to your grass type if you want a more tailored figure.

Most turf extension guidance favors fewer, deeper sessions over daily light ones, commonly two to three times a week, since it encourages deeper root growth and most soils cannot absorb a full weekly target in one sitting without runoff. This calculator defaults to 2 sessions a week and lets you change it, recalculating the per-session run time to still hit your weekly target.

Because zones are rarely identical. A rotor-head zone needs roughly three to four times the run time of a spray-head zone to deliver the same depth of water, and a larger area needs more total gallons even at the same run time as a smaller one. Run this calculator separately for each zone with its own head type and area rather than assuming one run time fits every zone on a controller.

This calculator sizes sprinkler run time for turf: area and application rate, in inches per hour, feeding into how long to run a spray or rotor zone. The Drip Irrigation Calculator sizes a drip system instead, adding up individual low-flow emitters in gallons per hour and checking whether that total fits your tubing and water source. They cover two genuinely different watering methods with different math behind each.

This calculator answers how long to run a sprinkler zone you already have, given its head type and area. The Lawn Watering Calculator answers a different question first - how much water your specific grass type actually needs per week and how often - which you can then bring back here as the target depth for a sprinkler-specific run-time answer.

No. This calculator works from the area a zone covers and its head type's application rate, not a head count, since application rate is what actually determines how fast water lands on the ground regardless of how many heads share the job of applying it evenly across that area.

Use the default for your head type - spray or rotor - which is prefilled from Colorado State University Extension's published ranges the moment you pick one. For an exact figure, run a simple catch-can test: place a few identical straight-sided containers across the zone, run it for 15 minutes, average the depth collected, and multiply by 4 to get inches per hour. Enter that measured number using the custom option above.