Drip Irrigation Calculator
Plan a home drip system. Enter your plants, emitters and watering goal to get total system flow (GPH), how long to run each session, how many zones your water source can feed, and weekly water use and cost — with emitter and schedule tables and a downloadable PDF report.
| Emitter | System GPH | Run/session | Zones |
|---|---|---|---|
| Enter your layout to compare emitters | |||
| Days/week | Water/session | Run/session | Weekly runtime |
|---|---|---|---|
| Enter your goal to compare schedules | |||
How to use the drip irrigation calculator
Four quick steps turn your planting into a working drip schedule — total emitters, system flow, run time per session, zones, and weekly water and cost — with comparison tables and a downloadable report.
Set the layout
Enter how many plants, emitters per plant, and the emitter flow (GPH). That sets total emitters and system flow.
Set the watering goal
Give the gallons each plant needs per week and how many days a week you’ll water.
Add source & cost
Enter your tap’s flow (GPM) and water price. The tool checks how many zones your source can feed.
Read results & save a PDF
Get run time per session, zones, and weekly water and cost, with emitter and schedule tables — then download a report.
How the schedule is calculated
System flow comes from the emitters; run time splits the weekly target across your watering days and divides by each plant’s flow; zones check that against your source. Here is the exact math.
Worked example — 30 plants, 2 × 1-GPH emitters each, 7 gal/plant/week over 3 days, 5 GPM source
Total emitters: 30 × 2 = 60 · System flow: 60 × 1 = 60 GPH
Water/session: 7 / 3 = 2.3 gal · Run: 2.3 / (2×1) × 60 ≈ 70 min
Source: 5 GPM × 60 = 300 GPH → 60 / (300×0.9) < 1 → 1 zone
Weekly: 30 × 7 = 210 gal · Cost at $5/1k: $1.05
≈ 70 min/session · 1 zone · 210 gal/week · about $1.05. Then adjust to your plants.
Drip irrigation reference charts
Handy lookups for emitter flow, source capacity, and rough weekly water by plant type. These are planning ranges — soil, sun, and season shift real needs.
| Emitter | Delivers | Good for |
|---|---|---|
| 0.5 GPH | ½ gal per hour | Small plants, tight spacing, clay soil |
| 1 GPH | 1 gal per hour | Most perennials and small shrubs |
| 2 GPH | 2 gal per hour | Shrubs, faster watering |
| 4 GPH | 4 gal per hour | Trees, large or thirsty plants |
Higher flow waters faster but draws more at once — check the total against your source before choosing.
| Source | Flow | Usable (90%) | 1-GPH emitters |
|---|---|---|---|
| Low hose bib | 4 GPM (240 GPH) | 216 GPH | ~216 |
| Typical hose bib | 5 GPM (300 GPH) | 270 GPH | ~270 |
| Strong hose bib | 6 GPM (360 GPH) | 324 GPH | ~324 |
If your system needs more flow than the usable source, split it into zones that run one at a time.
| Plant type | Per plant / week |
|---|---|
| Small plants / perennials | 3–5 gal |
| Shrubs | 5–10 gal |
| Small trees | 10–15 gal |
| Vegetables | varies by crop & stage |
Starting points only — more in summer heat, less in cool months. Group plants with similar needs on one zone.
Everything the calculator works out
A planting and a goal give you a full drip schedule — flow, run time, zones, and cost — with comparisons so you can tune it before you buy.
Key figures behind a drip plan
Built for planning a drip system
From a first raised bed to a whole yard, the same calculator turns plants and emitters into a working schedule.
Just installed drip and needs a starting run time and watering days to program the timer.
- Enter plants & emitters
- Set a weekly water goal
- Program the run time
Switching from sprinklers and wants to see weekly gallons and cost before and after.
- Enter your water price
- Compare emitter sizes
- Read weekly water & cost
Laying out a bigger system and needs to know if the tap can feed it or how many zones to split.
- Enter source flow (GPM)
- Check zones needed
- Split the schedule per zone
7 tips for a healthy drip system
The math gives a starting schedule; your plants give the final word. These points keep the plan realistic and the garden thriving.
Drip irrigation calculator FAQ
The run time, flow, and watering questions people ask most when planning a drip system.
Run time per session is the water each plant should get that session divided by its emitter flow.
Split the weekly target across watering days: water/session = weekly gal ÷ days. Then divide by the plant’s combined output (emitters × GPH) and convert to minutes.
Example: 7 gal/week over 3 days ≈ 2.3 gal/session; with two 1-GPH emitters (2 GPH), that’s 2.3 ÷ 2 × 60 ≈ 70 min. Start there and adjust to the soil.
Emitters are rated in gallons per hour (GPH) — commonly 0.5, 1, 2, or 4. A 1-GPH dripper running an hour delivers one gallon.
System flow is every emitter added up: total emitters × emitter GPH. So 30 plants with two 1-GPH emitters each is 60 emitters at 60 GPH — 1 gallon per minute while running.
Higher-flow emitters water faster but draw more at once, which matters against your tap’s supply.
It depends on source flow. A typical hose bib delivers about 4–6 GPM (240–360 GPH), and you should use only ~90% to leave headroom for pressure loss.
Divide system flow by usable source flow to see if it fits. If it needs more, split into zones that run one at a time: zones = system GPH ÷ (90% of source GPH), rounded up.
A 60-GPH system on a 300-GPH bib fits in one zone; a 600-GPH system would need two.
A zone is a section that runs on its own so total flow never exceeds what your source can supply.
Run every emitter at once beyond the tap’s capacity and pressure drops — the far emitters starve. Splitting into zones, each running separately (usually on a timer), keeps every emitter at its rated output.
The calculator sizes zones as system flow ÷ 90% of source flow, rounded up. More zones repeat the schedule per zone, so weekly runtime rises.
Long enough to deliver each plant’s target for the session — then adjusted by what the soil and plants tell you.
The math gives a starting time, but real needs shift with plant type, soil, sun, and season; plants want far more in hot, dry summer. Deep, infrequent watering builds stronger roots than daily sprinkles, except in sandy soil.
Use the calculated time as a baseline, check soil moisture a few inches down after a cycle, and adjust.
Two to three days a week is a common start for established plants, with the weekly total split across those days.
Fewer, longer sessions push water deeper and build deeper roots — good for shrubs and trees. More frequent, shorter sessions suit shallow-rooted plants and sandy soil. New plantings need more frequent watering until established.
Fewer days means a longer run each time for the same weekly total — the calculator shows both so you can compare.
Weekly use is plants × weekly target per plant. Thirty plants at 7 gal each is 210 gallons a week.
Because drip delivers straight to the root zone with almost no evaporation or runoff, it typically uses far less than sprinklers. For cost, multiply weekly gallons by your price per 1,000 gallons — 210 gal at $5/1,000 ≈ $1.05 a week.
Use rises in summer heat and drops in cooler months, so treat this as a warm-season baseline.
As a rough warm-season guide: small plants and perennials about 3–5 gal/week, shrubs 5–10, small trees 10–15. Vegetables vary widely by crop and stage.
These are starting points — actual needs depend on plant, climate, soil, and sun. Group plants with similar needs on the same zone so they can share a schedule.
Set a target, run the calculator for a baseline, then let the plants and soil fine-tune it over the first few weeks.
Estimate only — adjust to your plants and weather. Figures use US units (GPH, GPM, gallons, minutes). Water needs vary with plant type, soil, sun, and season, and emitter output changes with water pressure, so these results are a starting schedule, not a fixed prescription. Use the calculated run time as a baseline, then check soil moisture and watch how your plants respond, raising or lowering the time as needed. If system flow exceeds what your source can supply, split the system into the number of zones shown so every emitter gets its rated flow. For planning purposes only.