Landscaping
Irrigation Calculator
Work out sprinkler run times and water use to deliver the right amount of water each week.
Result
Assumes even coverage and no rainfall. Measure your real precipitation rate with catch cans rather than trusting the head's rating. Actual output varies with pressure and spacing.
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About this calculator
How much water does a lawn need?
About an inch a week including rainfall for most cool-season grasses, delivered in two or three deep soakings rather than daily sprinkles. Deep watering drives deeper roots.
How do I find my sprinkler's precipitation rate?
Put several straight-sided containers around a zone, run it for 15 minutes, measure the depth collected and multiply by four. That gives inches per hour as actually delivered.
The formula
run time = (weekly inches ÷ precipitation rate) ÷ watering days; gallons = sq ft × inches × 0.623
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