Irrigation Water Calculator — Formula
## How to Calculate Irrigation Water Needs
Lawns and gardens need about 1 inch of water per week, including rainfall.
### Formula
**Weekly Gallons = Area * (Need - Rainfall) * 0.623 / Efficiency**
### Irrigation Efficiency
- Drip irrigation: 85-95%
- Sprinkler: 60-75%
- Flood/furrow: 40-60%
Overwatering is the most common irrigation mistake, wasting both water and money.
Lawns and gardens need about 1 inch of water per week, including rainfall.
### Formula
**Weekly Gallons = Area * (Need - Rainfall) * 0.623 / Efficiency**
### Irrigation Efficiency
- Drip irrigation: 85-95%
- Sprinkler: 60-75%
- Flood/furrow: 40-60%
Overwatering is the most common irrigation mistake, wasting both water and money.
Exemplo Resolvido
3,000 sq ft lawn needing 1 inch/week with 0.5 inches rain at 75% sprinkler efficiency.
- Water deficit: 1.0 - 0.5 = 0.5 inches
- Weekly gallons: 3,000 * 0.5 * 0.623 / 0.75 = 1,246 gallons
- Monthly: 1,246 * 4.33 = 5,395 gallons
- Season (26 weeks): 1,246 * 26 = 32,396 gallons