Drip Irrigation Calculator — Tubing, Emitters & Flow
Plan a drip system by entering your garden rows, plant spacing, and emitter choice. This calculator gives you the tubing length, the number of emitters and fittings, and the total flow rate so you can size your system.
How to use this calculator
- Enter how many rows you have and how long each row is, in feet.
- Set the plant spacing — the distance between plants along a row.
- Choose how many emitters each plant gets (large plants often want two) and the emitter flow rate.
- Check the total flow stays within your faucet/timer capacity (a typical hose bib supplies 200+ GPH).
The formula
A drip system is sized by plant count, tubing length, and total flow.
Plants per row = row length (in) ÷ spacing (in) + 1. Total plants = plants per row × rows.
Emitters = total plants × emitters per plant. Tubing ≈ rows × row length, plus ~10% for runs back to the manifold.
Total flow (GPH) = emitters × emitter flow rate. Keep this under your water supply and timer rating.
Worked example
4 rows, 25 ft each, plants every 18 in, 1 emitter/plant at 1 GPH.
Plants per row = (25 × 12) ÷ 18 + 1 = 17.7 → 17 + 1 ≈ 17 plantsTotal plants = 17 × 4 = 68 plantsEmitters = 68 × 1 = 68 emittersTubing = 4 × 25 × 1.1 = 110 ftFlow = 68 × 1 = 68 GPH
You need about 110 ft of tubing, 68 emitters, and a supply that delivers at least 68 GPH.
Frequently asked questions
How much drip tubing do I need?
Multiply the number of rows by the row length, then add about 10% for the runs connecting rows to the manifold. For 4 rows of 25 ft that is roughly 110 feet.
How many emitters per plant?
One emitter suits most vegetables and small plants. Use two emitters for shrubs and larger plants so the root zone is watered evenly on both sides.
What flow rate should I use?
Emitters commonly come in 0.5, 1, and 2 GPH. Lower rates suit clay soil (water spreads slowly), higher rates suit sandy soil. Keep total flow within your faucet and timer rating.