How we got these numbers
Enter area and flow to see the step-by-step.
Formulas
- PR (US) = (Total GPM × 96.3) ÷ Area(ft²) • (Metric) = (L/min × 60) ÷ Area(m²)
- Effective PR = PR × DU
- Run-time (hr) = Target depth ÷ Effective PR
- Depth = Run-time × Effective PR
- Volume (US) = Area(ft²) × Depth(in) × 0.623 • (Metric) = Area(m²) × Depth(mm)
Example
Sprinklers: 25 GPM over 43,560 ft² (1 acre), DU 0.75, target 0.5 in:
- PR = (25 × 96.3) ÷ 43,560 ≈ 0.055 in/hr
- Eff PR = 0.055 × 0.75 ≈ 0.041 in/hr
- Run-time = 0.5 ÷ 0.041 ≈ 12.1 hr
- Gallons = 43,560 × 0.5 × 0.623 ≈ 13,575 gal
Notes
- Drip: use total GPH (US) or L/h (metric); calculator converts to GPM/L/min for PR.
- If run-time is long, split into cycles to reduce runoff.
- Adjust DU from a catch-can test for better accuracy.
Estimates only. Verify with local irrigation guidance for your soils and slopes.
Prepared by AgCalculator · Last updated October 27, 2025