Drip irrigation calculator

Enter your plants, emitters and watering schedule. You'll see how much water the zone uses and whether your faucet can supply it.

Number of plants

Emitters per plant

Emitter flow

Run time per watering (hours)

Waterings per week

Water supply (gallons per minute)

–gallons per hour for this zone

Zone flow (GPM): –
Gallons per watering: –
Gallons per week: –
Max emitters on one zone: –

Max emitters uses 80% of your supply flow, leaving a safety margin.

How to measure your water supply

Time how long it takes to fill a 5 gallon bucket from the faucet you'll connect to, with the tap fully open. Divide 5 by the number of seconds, then multiply by 60. If the bucket fills in 60 seconds, your supply is 5 gallons per minute.

How the math works

Plants times emitters times the emitter flow gives the zone's gallons per hour. Thirty plants with two 1 GPH emitters each use 60 gallons per hour, which is 1 gallon per minute. Running for an hour three times a week, that's 180 gallons per week.

Choosing emitter size

Soil	Emitter flow
Clay, which absorbs slowly	0.5 GPH
Loam	1 GPH
Sandy, which drains fast	1–2 GPH

Keep emitters on one zone the same size so every plant gets a predictable amount.

Common questions

How long should drip irrigation run?

Much longer than sprinklers, because drip puts water down slowly. An hour or more per session is common. Check by digging a few inches beside a plant a day after watering. The soil should be moist at root depth.

What happens if a zone has too many emitters?

Pressure drops, and emitters at the far end of the line barely drip. Split the garden into two zones or use lower-flow emitters.