Free tool
Watering Calculator
Most lawns are overwatered on a fixed timer schedule that never adjusts for rainfall. Enter your target, recent rainfall, and sprinkler output to get an exact run time instead.
Run time per session
75 min
Total run time this week
150 min
Water still needed
1.25 in
How this is calculated
Water still needed = weekly target − rainfall already received. Total run time = (water still needed ÷ sprinkler output rate) × 60 minutes, split evenly across your weekly sessions.
Don't know your sprinkler's output rate? Set out a few straight-sided containers (a tuna can works), run the sprinkler for 15 minutes, measure the depth collected, and multiply by 4 to get inches per hour. See our watering guide for the full method.