A timer setting describes duration, while a crop water plan describes volume. The link between them is the flow delivered by all emitters running together. Without that flow figure, choosing a number of minutes is only a guess.
Use Drip Irrigation Runtime Calculator when you have a net water target for one session. Enter the number of simultaneously operating emitters, flow per emitter and the application efficiency you are assuming. The tool converts net litres to gross applied litres before calculating duration.
A 120 litre net watering session
Suppose the root zone target is 120 litres and application efficiency is 90%. Gross applied water is 120 divided by 0.9, or about 133.333 litres.
With 60 emitters delivering 2 litres per hour each, the zone flow is 120 litres per hour. Dividing gross water by that flow gives about 1.111 hours, or 66.667 minutes. The numerical result is an estimate under the stated constant flow and efficiency assumptions.
If the required net litres are zero, calculated runtime is zero. Emitter count and emitter flow still need valid positive entries because they define the zone rather than a missing or nonworking system.
Count only what runs in this session
A garden may contain 100 emitters but use them across several separately operated zones. Entering all 100 for a session that runs only 60 would overstate flow and shorten the calculated duration.
Use delivered flow at the relevant operating conditions. A nominal emitter marking may not match a partially blocked, poorly supplied or otherwise different installation. The worksheet cannot measure pressure or verify the flow uniformity of the actual lines.
When emitters have different flow rates, Drip Zone Flow Calculator can total them as separate line groups. A single average flow entered here should represent the emitters actually being counted, not an unrelated supplier example.
Avoid counting efficiency twice
The litres field is the desired net session water, before application losses. If you already have a gross water figure from Crop Water Budget Calculator, do not divide it by the same efficiency again. Transfer the relevant net requirement, or use 100% here when deliberately timing a known gross delivery volume.
The calculation does not determine whether one uninterrupted run causes runoff or whether irrigation should be split into shorter sessions. It also does not assess pump limits or uneven wetting. Check the physical garden while using the duration as a volume conversion.
Save the flow assumptions with the result. A timer that was correct for one zone or season should not be reused after the emitter count, delivery flow or session target has changed.