Understanding your result
Run time is shared by the whole zone. Adding identical plants increases the required total flow and total volume together, so it does not change run time if the system maintains the stated emitter output. Weekly volume multiplies one session by the selected number of sessions.
For emitter labels in gallons per hour, use the Flow Rate Converter before entering liters per hour here.
To compare this demand with roof runoff, use the Rainwater Harvesting Calculator and allow for storage limits between rainfall events.
The formula
Zone flow equals emitter output × emitters per plant × plant count. Divide the plant target by the efficiency fraction to allow for water that does not reach the intended target. An efficiency of 100% applies no adjustment. This fraction is an assumption supplied by you, not a measured irrigation rating.
Worked example
Twenty plants each need 2 L per session. Each has two 2 L/h emitters. The zone delivers 80 L/h and needs 40 L, giving 30 minutes per session. Three sessions use 120 L per week. An assumed 80% effective delivery raises runtime to 37.5 minutes.
How to use this calculator
- Choose a target volume per plant for one watering session.
- Read the emitter rating in L/h and enter emitters per plant and plant count.
- Enter an efficiency assumption and weekly session count, then check runtime and supply flow.
Start with a watering target
This calculator schedules a volume you have already chosen. It does not prescribe water needs from plant names. Root depth, soil, containers, rainfall, season, and plant size can change that target. Recheck soil moisture after a trial run before relying on an unchanged timer setting.
Check actual emitter delivery
Emitter ratings apply at specified operating conditions. A zone that exceeds the supply flow, has blocked outlets, or has pressure variation may deliver unevenly. A simple timed collection at several outlets can reveal differences that a label alone will not show. University extension guidance emphasizes matching drip equipment to water supply and pressure.
Use separate zones for different requirements
The calculation assumes every plant receives the same number of identical emitters. Split beds with different targets into separate calculations or use appropriately selected emitter combinations. A single average flow may hide an under-watered plant even when the total liters look correct.
Assumptions & limitations
What this calculation assumes
- All emitters run together at a constant supplied flow rate.
What to keep in mind
- Does not model pipe pressure losses, pump sizing, soil infiltration, or crop water requirements.
Common questions
Does doubling plant count double run time?
Not when each added plant also gets the same emitter arrangement and rated flow is maintained. Zone flow and total water both double.
Can I enter gallons per hour directly?
Convert to liters per hour first; one US gallon is 3.785411784 liters. The linked flow converter distinguishes units.