Watering Schedule Calculator
Build a watering schedule with the right volume, frequency and duration for your garden.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Plan a rough weekly irrigation amount from fixed plant, soil and temperature factors, then subtract entered rainfall. The coefficients and number of weekly sessions are heuristics, not a crop-specific prescription; local weather, growth stage, mulch, drainage and soil moisture can change needs. Enter the combined emitter flow for the whole zone in gallons per hour.
Worked example
calculated with the default values below
Garden area 200 sq ft · Plant type Vegetables (1 in/week) · Soil type Loam (1×) · Average temperature 75 °F · Rainfall this week (in) 0.5 in · Combined emitter flow for this zone (gal/hour) 4 gal/h Gross weekly target 124.6 gal · Supplemental water after rainfall 62.3 gal · Sessions per week 3 · Minutes per session 312 min
General background references
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
I = P × S × k_T; W_s = max(0, A × (I − R) × 0.623); t = W_s ÷ q ÷ N
- P
- Plant factor: 0.5–1.5 by type
- S
- Soil factor: sand 1.2, loam 1, clay 0.8, potting 1.3
- k_T
- Temperature factor: 0.8 / 1 / 1.15 / 1.3
- A
- Area (sq ft)
- R
- Rainfall (in/week)
- N
- Sessions per week
q is combined zone flow in US gal/hour; minutes/session = supplemental US gal ÷ q ÷ sessions × 60. Sessions are heuristic; not crop-specific guidance.
Frequently asked questions
How are weekly irrigation and run time estimated?
The model applies fixed plant, soil and temperature factors to an inches-per-week target, subtracts entered rainfall, and converts depth to gallons using 0.623 gal per sq ft per inch. It divides supplemental water across a heuristic 2, 3 or 7 sessions; emitter flow is entered in gallons per hour. These are planning assumptions, not crop-specific advice. A one-inch weekly target is only a starting point in some extension guidance; actual needs vary. [University of Minnesota Extension](https://extension.umn.edu/agriculture/specialty-crops/vegetable-farming/digging-or-expanding-a-well).