Enter your emitter count, flow rate and each plant’s weekly water target to get run time per session, system flow and total gallons.
The formula
Each session must deliver weekly target ÷ waterings per week gallons to every plant. With one emitter per plant, run time = gallons per session ÷ emitter GPH × 60 minutes. The calculator also totals system flow (emitters × GPH) so you can check your supply line and zone capacity.
Worked example
30 plants on 1 GPH emitters, each needing 2 gallons a week across 3 waterings: 0.67 gal per session ÷ 1 GPH = 40 minutes per watering. The zone flows 30 GPH and uses 60 gallons a week.
Dialing it in
Fewer, deeper waterings beat daily sips — roots follow the moisture down. Sandy soil drains fast and prefers three shorter sessions; clay holds water and does better with two longer ones. Watch the first inch of soil the morning after a session: still soggy means shorten the run, bone dry means lengthen it. Multiple emitters per large plant simply divide the run time accordingly.