Drip Irrigation Calculator
Design a drip system: how many emitters, how much tubing and how long to run it.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Estimate emitter count, total flow, tubing, and weekly runtime from row dimensions, emitter spacing and flow, and water need. The model uses US customary units and caps each zone at 200 gallons per hour as a planning assumption. Check tubing pressure limits and your site’s flow.
Worked example
calculated with the default values below
Row length 30 ft · Number of rows 4 · Emitter spacing 12 in · Flow per emitter 0.5 gal/h · Row spacing 2 ft · Water need per week 1 in Emitters per row 30 · Total emitters 120 · Mainline tubing needed 128 ft · Total flow 60.0 gal/h · Run time per week 150 min · Zones needed (200 gal/h limit) 1
Method and assumptions
t = 60 × 0.623 × L × d × n × w ÷ (q × n × ⌊12L ÷ p⌋) t is weekly run time (min); 0.623 converts inches of water over ft² to gallons. Zones = max(1, ceil(zone flow ÷ 200 gal/h)); emitters per row rounded down. Estimate emitter count, total flow, tubing, and weekly runtime from row dimensions, emitter spacing and flow, and water need. The model uses US customary units and caps each zone at 200 gallons per hour as a planning assumption. Check tubing pressure limits and your site’s flow. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Data sources
Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Disclaimer
These are general gardening estimates. Planting windows, growth, water and nutrient needs vary by place and plant. Check local extension guidance and product labels before acting on an estimate.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
t = 60 × 0.623 × L × d × n × w ÷ (q × n × ⌊12L ÷ p⌋)
- L
- Row length (ft)
- d
- Row spacing (ft)
- n
- Number of rows
- w
- Weekly water need (in)
- q
- Flow per emitter (gal/h)
- p
- Emitter spacing (in)
t is weekly run time (min); 0.623 converts inches of water over ft² to gallons. Zones = max(1, ceil(zone flow ÷ 200 gal/h)); emitters per row rounded down.
Frequently asked questions
Why are zones split when total flow passes two hundred gallons per hour?
The tool caps each irrigation zone at 200 gallons per hour, because standard half-inch tubing loses pressure past that flow, and it divides your total emitter flow by that limit to set the zone count. With 4 rows of 30 feet at 12 inch spacing and 0.5 gal/h emitters you get 120 emitters and 60 gal/h, fitting one zone, but raising emitter flow to 2 gal/h pushes flow to 240 gal/h and forces a second zone. Run time then comes from weekly gallons divided by zone flow times 60.
Which inputs and limits apply to Drip Irrigation Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Row length: 1–2,000 ft; Number of rows: 1–200; Emitter spacing: 6–48 in; Flow per emitter: 0.1–5 gal/h; Row spacing: 0.5–20 ft; Water need per week: 0.1–4 in t = 60 × 0.623 × L × d × n × w ÷ (q × n × ⌊12L ÷ p⌋) t is weekly run time (min); 0.623 converts inches of water over ft² to gallons. Zones = max(1, ceil(zone flow ÷ 200 gal/h)); emitters per row rounded down. Estimate emitter count, total flow, tubing, and weekly runtime from row dimensions, emitter spacing and flow, and water need. The model uses US customary units and caps each zone at 200 gallons per hour as a planning assumption. Check tubing pressure limits and your site’s flow. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
What is a complete worked example for Row length = 30 ft; Number of rows = 4?
Inputs: Row length = 30 ft; Number of rows = 4; Emitter spacing = 12 in; Flow per emitter = 0.5 gal/h; Row spacing = 2 ft; Water need per week = 1 in. Calculation: t = 60 × 0.623 × L × d × n × w ÷ (q × n × ⌊12L ÷ p⌋). Results: Emitters per row = 30; Total emitters = 120; Mainline tubing needed = 128 ft; Total flow = 60.0 gal/h; Run time per week = 150 min; Zones needed (200 gal/h limit) = 1.