Inputs
Bed area, plot area, or irrigated area.
We normalize to square feet.
Sets typical crop water need in inches/week (ET + management).
Overrides the dropdown if edited.
Lower efficiency = more water needed.
Inches/week that effectively reaches roots.
Adjust for storms, runoff, infiltration.
Weeks for your crop cycle or planning season.
Used to compute gal/day on watering days.
Optional: Rainwater harvesting
Roof/shed/tarp area capturing rain.
Catchment unit.
Average inches/month for capture estimate.
Losses from first-flush, overflow, leaks.
Planning-level tool.
“Inches/week” is a common way to express crop water requirement. This calculator converts inches of water over your area into gallons,
subtracts effective rainfall, and adjusts for irrigation efficiency.
Results
Net irrigation after rainfall, adjusted for efficiency.
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Gallons per watering day
—
Gallons per week
—
Gallons per season
Water budget breakdown
| Component | Inches / week | Gallons / week |
|---|---|---|
| Crop requirement | — | — |
| Effective rainfall | — | — |
| Net irrigation (before efficiency) | — | — |
| Efficiency adjustment (losses) | — | — |
—
Rainwater harvesting estimate
If you capture rain from a roof or tarp, this estimates monthly gallons captured and how it compares to your weekly irrigation need.
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Gallons captured / month
—
Equivalent / week
—
Suggested storage (1–2 weeks)
— of weekly need covered
— gal/week gap (after capture)
Formula used: Gallons = inches × sqft × 0.623. Capture adds an efficiency factor.
Quick guidance
- If effective rainfall is high, irrigation demand drops sharply—especially with drip/subsurface drip.
- For island resilience, storage sized to 1–2 weeks of irrigation helps bridge dry spells.
- Using mulch, shade cloth, windbreaks, and healthy soil can reduce effective inches/week needed.