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Drip irrigation emitter above a clear jug beside potted plants

Water / measured inputs

Cannabis Irrigation Water Use Calculator

Turn your irrigation schedule into a clear water budget. Work from measured flow, see every multiplier, and keep a complete record.

Browse Grow toolsUse the calculator
01 / Your schedule

Enter your numbers

Water per event is the amount for one plant position. All volumes use US gallons.

Work out water per eventMeasured dripper flow × drippers × runtime

Start with a one-minute catch.

At normal operating conditions, collect one dripper’s output for 60 seconds and measure the milliliters. Repeat across the system and enter a representative average.

Use a separate estimate for zones with different emitters or schedules. This helper assumes equal average flow and does not test distribution uniformity.

Water per plant, per eventmL/min × drippers × minutes÷ 3,785.411784 = US gallons
Delivered water per plant / event—Enter your measurements to preview a volume.

Delivered water is not net utility demand. Applying this value assumes the delivered water is fresh supply, without a recapture adjustment. For a recirculating system, keep measured net replacement water in the main input instead.





What it calculates
Use the result as a scenario, not a black box
Turn an irrigation schedule into a facility water-use estimate. Enter plant positions, water per event and events per day to calculate daily, weekly and monthly gallons plus an optional utility-cost estimate.
The water-use calculator is designed for budgeting and infrastructure planning. It does not tell you how much to irrigate a plant. Instead, you enter the schedule you already use or intend to test and the tool converts it into facility-level water demand.
How the math works
Daily gallons = plant positions × gallons per event × events per day. Weekly gallons = daily gallons × 7. Period gallons = daily gallons × operating days. Utility estimate = period gallons ÷ 1,000 × water/sewer rate.
Example
One hundred positions receiving 0.5 gallons once per day use 50 gallons per day, 350 gallons per week and 1,500 gallons over a 30-day period. At $8 per thousand gallons, the direct water/sewer estimate is $12 before other fees.
Plan the surrounding system with Hydroponic growing mediums, Hydroponic water pumps and Cannabis nutrients.
Budget electrical use separately with Lighting Cost and HVAC Load.
The measured-flow helper converts volume and runtime; it does not recommend an irrigation schedule. Read UC ANR on measuring emitter discharge and NIST’s US gallon conversion table.



FAQ
Questions about this calculator
Does the calculator recommend watering frequency?
No. It only converts the schedule you enter into water-use totals.
Can I model recirculating systems?
Yes, but enter the net replacement water rather than total recirculated flow if you want a utility-demand estimate.
Why include sewer cost?
Many commercial water bills bundle water and sewer charges, so the user-entered rate can represent the combined effective cost.


Keep the room plan connected
Space, supply and moisture.
Take each assumption to the tool that can test it.
Space planningCanopy & SpacingCheck the area and plant-position assumptions.Facility planningGrow Room BuilderBring space, fixtures and operating inputs together.Moisture planningDehumidifier SizingEstimate removal from a separate moisture-load input.