Grounds ToolkitIrrigation and Water
How Long Should This Zone Run to Apply the Right Amount of Water?
Enter your zone's precipitation rate and a target weekly depth. This works out the runtime needed, and estimated gallons if you add the zone's area.
How this is calculated
Runtime is target depth divided by precipitation rate, converted to minutes. If a zone area is entered, estimated volume applied comes from a standard conversion: one inch of water over 1,000 sq ft is about 623 gallons.
Worked example
A zone with a 0.5 in/hr precipitation rate targeting 1 inch of water this week needs 120 minutes of total runtime. Over a 2,000 sq ft zone, that applies about 1,247 gallons.
Frequently asked questions
Where do I find my zone's precipitation rate?
It's usually on the sprinkler head or nozzle spec sheet, or the controller's installation documentation. It varies too much by head type and spacing for one default to be useful, so this calculator asks for it directly.
Why does the default target depth say 1 inch per week?
That's the commonly cited university extension guideline for turf in active growth, but it varies by climate and grass type, some regions need as little as 0.5 in/week and others up to 1.5. Change it to match your local guidance.
Should I run this all in one session?
Not necessarily. The total runtime is correct either way, but splitting it into 2 or 3 shorter sessions across the week reduces runoff on clay or compacted soil, especially for the higher end of the depth range.