💧 Irrigation Run Time Calculator

Calculate how long to run your irrigation system to apply a target water depth. Accounts for flow rate and application efficiency.

Enter target depth, area, flow rate, and efficiency to find required run time in hours and minutes.

📊 Results

Run Time (hours)-

Run Time (minutes)-

Water Applied (gallons)-

Water per Acre (gallons)-

🧮 Formula & How It Works

Run Time (hr) = (Depth in × Area acres × 27,154) ÷ (GPM × 60 × Efficiency%)

27,154 = gallons in one acre-inch.

📊 Calculation Example

1 inch to 10 acres at 500 GPM, 80% efficiency: Time = (1×10×27,154)÷(500×60×0.80) = 11.31 hr = 679 min. Water = 339,425 gal.

📖 How to Use This Calculator

1. Target depth from ET or soil moisture. 2. Area. 3. Measured flow rate. 4. Efficiency (70-90% sprinkler, 85-95% drip). Calculate.

🌾 About This Tool

Proper scheduling ensures adequate water without waste. Over-irrigation wastes water and leaches nutrients.

⚠️ Common Mistakes & Tips

Using rated GPM not measured (often 10-20% lower). Ignoring efficiency. Applying faster than infiltration rate causes runoff.

✓ Expert Reviewed: This calculator and its content have been reviewed by agricultural experts. Formulas are based on standard extension service recommendations.

📚 References & Sources

FAO (Food and Agriculture Organization) — Agricultural production and nutrition guidelines
USDA NRCS — Field Office Technical Guide and conservation practice standards
Land-Grant University Cooperative Extension System — crop and livestock recommendations

❓ Frequently Asked Questions

What is 27,154? ▼

Gallons in one acre-inch: 43,560 sq ft × 1/12 ft × 7.48 gal/cu ft.

What efficiency to use? ▼

Drip 85-95%, center pivot 75-85%, sprinkler 65-75%, flood 50-70%.

How often to irrigate? ▼

When soil moisture drops to 50% available water. Use sensors or ET scheduling.