Lawn Watering Calculator (Sprinkler Run Time)
Enter your weekly target, the sprinkler’s output and the lawn area.
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Lawn Watering Calculator (Sprinkler Run Time) by TheCalcTools
How the Lawn Watering Calculator (Sprinkler Run Time) works
One inch of water over 1,000 sq ft is about 623 US gallons. The run time is the water still needed after rain divided by your sprinkler’s output rate.
Deep, infrequent watering encourages deeper roots than daily sprinkling. Water early in the morning to cut evaporation.
The formula
Worked example
Using the default values shown in the calculator:
| Water needed per week (inches) | 1 |
|---|---|
| Rain expected this week (inches) | 0.3 |
| Sprinkler output (inches per hour) | 0.5 |
| Lawn area (sq ft) | 3000 |
| Watering days per week | 2 |
- Needing 0.7 in after rain, at 0.5 in/hour: 84 minutes a week (42 per day over 2 days).
- That uses 1,309 gallons on 3,000 sq ft.
Result:
| Total run time per week (minutes) | 84 |
|---|---|
| Minutes per watering day | 42 |
| Water used per week (US gallons) | 1,309 |
| Litres per week | 4,956 |
Frequently asked questions
How do I measure sprinkler output?
Place several straight-sided cans across the lawn, run the sprinkler for 15 minutes, average the depth and multiply by 4 for inches per hour.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.