Garden Watering Schedule Calculator
Converting "An Inch of Water" Into Gallons
The standard watering guideline — about an inch of water per week, including rainfall — is easy to say and hard to apply with a hose or watering can, since neither measures in inches. This calculator converts that inch-based target into actual gallons for a given garden area, then splits it across however many times a week you water.
The Formula
Water per Session = Weekly Water Needed ÷ Frequency per Week
The constant 0.623 converts one inch of water depth over one square foot into gallons: one cubic foot holds 7.48 gallons, and one inch over one square foot is 1⁄12 cubic foot, so 7.48 ÷ 12 ≈ 0.623 gallons per square foot per inch.
Worked Example
A 300 sq ft vegetable garden, watered twice a week to a total of 1 inch:
| Quantity | Value |
|---|---|
| Total weekly water | 186.9 gallons |
| Water per session | 93.45 gallons |
Adjusting the Baseline
- Hot, dry climates or sandy soil — often need more than the 1 in/week baseline, and more frequent, lighter sessions since sandy soil drains fast.
- Clay soil or cooler weather — may need less frequent, deeper watering, since clay holds moisture longer and over-watering risks root rot.
- Container and raised-bed gardens — typically dry out faster than in-ground beds and often need watering checked more often than the baseline weekly rule suggests.
How to Use This Calculator
- Enter the garden area in square feet.
- Enter the target water depth per week in inches (defaults to 1, the common baseline).
- Enter how many times per week you plan to water (defaults to 1).
- Select Calculate to get total weekly gallons and gallons per watering session.
Related Calculations
Newly fertilized beds often need adjusted watering — see the Garden Fertilizer Calculator. For mulch to help retain that moisture, check the Mulch Depth Calculator.