Lawn Watering Runtime Calculator (Minutes, Water Use & Cost)
Work out how long to run sprinklers to hit a target watering depth. Choose a method: enter your system’s precipitation rate, estimate it from flow & area, or use a catch‑can test. Outputs minutes per session, weekly minutes, estimated water use, and optional weekly cost. Metric & imperial supported.
How to use
- Choose units (Metric or Imperial).
- Select a method: Precipitation Rate, Flow & Area, or Catch‑can Test.
- Enter your target depth (per week) and sessions per week.
- (Optional) Add lawn area for water‑use and cost; set efficiency (distribution uniformity) if you want the tool to allow extra time for uneven coverage.
- Click Calculate. The tool shows minutes per session and other details.
Worked example
Metric, Flow & Area method: Zone area 50 m², total flow 20 L/min, target depth 25 mm/week, 3 sessions/week, efficiency 80%.
- Precipitation rate: 60 × 20 ÷ 50 = 24 mm/h
- Weekly minutes for 25 mm (with 0.8 efficiency): 25 ÷ (24×0.8) × 60 ≈ 78 min/week
- Per session (÷3): 26 minutes
- Water per session: 50 × (25/3) = 417 L; per week: 1,250 L
Lawn watering runtime calculator
FAQs
How do I find precipitation rate?
Manufacturers list it for the nozzle and spacing. You can also estimate it from flow & area or run a simple catch‑can test and measure the water depth after a timed run.
What target depth should I use?
Many lawns aim for about 25 mm (1 inch) per week in warm weather. Adjust for your grass type, restrictions and recent rainfall.
What does Efficiency / DU (%) mean?
Lower uniformity (e.g., 70–85%) means some spots get less water. The calculator multiplies the precipitation rate by this percentage, which increases the runtime so dry spots are covered.
How accurate is the Flow & Area method?
It’s a good estimate if your total zone flow and irrigated area are correct. For best accuracy, run a catch‑can test.