Irrigation Run Time Calculator
Calculate how long to run your sprinklers to hit your target water depth.
Watering target
Your schedule
Run time per session
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minutes
Water per session
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inches
Weekly total
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inches
Target water per week—
Sessions per week—
Water needed per session—
Sprinkler rate—
Soil absorption factor—
Run time per session—
How to find your sprinkler's precipitation rate
The easiest way is to place several straight-sided cans (tuna cans work well) around your lawn and run your sprinklers for exactly 15 minutes. Measure the water depth in each can and multiply by 4 to get inches per hour. Average the readings across all cans for a reliable figure.
Rotary heads typically deliver 0.5–1.0 inches per hour. Fixed spray heads are faster at 1.5–2.0 inches per hour. Drip and soaker systems are much slower — 0.2–0.5 inches per hour — but deliver water more efficiently directly to roots.
Frequently asked questions
How much water does a lawn need per week?
Most cool-season lawns need about 1 inch of water per week from rain and irrigation combined. Warm-season grasses like bermuda and zoysia often need 1–1.5 inches in summer. During cooler months or rainy spells, reduce irrigation accordingly.
Is it better to water deeply once or lightly every day?
Deep, infrequent watering is almost always better. It encourages roots to grow deeper into the soil, making your lawn more drought-resilient. Daily light watering keeps roots shallow and near the surface, making the lawn more susceptible to heat stress.
What time of day should I run my sprinklers?
Early morning (5–9 AM) is ideal. Water pressure is higher, wind is calmer, and the grass dries off before evening — reducing the risk of fungal disease. Avoid evening watering, which leaves grass wet overnight.
Why does soil type affect run time?
Clay soils absorb water slowly and can puddle or run off if watered too fast. Sandy soils drain quickly. The soil factor in this calculator adjusts your run time to account for absorption speed — clay users may need to run multiple shorter cycles rather than one long session to avoid runoff.