IrrigationForge

Drip Irrigation Calculator

Plan a drip system end to end: from bed size and plant spacing, get the number of plants and emitters, the total flow your valve must supply, the weekly water volume and the run time that delivers it.

Inputs

Result

US customary ⇄ metric
Plants in the bed-plants
Total emitters-emitters
Zone flow-GPH
Weekly water need-gallons/week
Run time to deliver it-minutes/week

Planning estimate - not a substitute for a pressure-tested engineering design.

Formula

Plants = area ÷ (plant spacing)². Zone flow = plants × emitters per plant × GPH. Weekly gallons = target inches × area × 0.6233 ÷ efficiency. Run time = weekly gallons ÷ zone GPH × 60.

Example

200 sq ft bed, 1.5 ft spacing, 1 GPH emitters, 1 per plant, 1 in/week target at 90%: ~88 plants → 88 GPH zone; 1 × 200 × 0.6233 ÷ 0.9 ≈ 138 gal/week → 138 ÷ 88 × 60 ≈ 94 min/week.

Assumptions

  • Uniform planting grid across the bed.
  • Emitters are pressure-compensating so line length does not skew flow.
  • One valve per hydrozone with similar plants; keep each valve's total GPH within its capacity.

Limitations

This tool is a planning aid for DIY design and pre-design work. It does not replace an on-site pressure and flow test, a catch-cup uniformity test, or local code and backflow requirements. For steep slopes, long pipe runs, large elevation changes or commercial-scale systems, have a qualified irrigation designer verify the plan before installation.

What This Means

Drip's ~90% efficiency versus ~70-75% for spray means the same plant need costs 15-25% less water - and watering at the root zone starves the weeds between rows.

Next Step

Schedule the sessions with the Drip Run Time Calculator, and budget the whole yard with the Water Budget Calculator.

Related Tools

Drip Irrigation Run Time Calculator Irrigation Water Budget Calculator Irrigation Run Time Calculator

Related Guides

Drip Emitter Flow TableReference table of drip emitter flow rates (GPH), how many emitters each plant type needs, and the weekly gallons that adds up to.

Sources

Frequently Asked Questions

How many drip emitters can one valve run?

Depends on supply: at 10 GPM and 1 GPH emitters, up to ~500 feet of capability - but in practice keep valves in the 100-300 GPH range and split beds accordingly.

Is drip really more efficient than sprinklers?

Yes - well-designed drip reaches 90%+ application efficiency versus roughly 70-75% for spray heads, because water leaves the line slowly at the root zone with little evaporation or overspray.