Lawn Watering Schedule Calculator
Calculate how much water your lawn needs per week and create a watering schedule.
Based on lawn size, grass type, and your local climate zone.
Most lawns need 1 to 1.5 inches (25–38 mm) of water per week during the growing season. This includes both rainfall and irrigation. Watering the right amount, not too little and not too much, is the key to a healthy, resilient lawn.
How the calculation works:
Water Volume = Lawn Area × Water Depth per Week
Irrigation Needed = Target Depth − Estimated Rainfall
For example:
- A 2,000 ft² (186 m²) lawn needing 1 inch (25 mm) of water per week:
- 2,000 × (1/12) = 167 cubic feet = 1,250 gallons = 4,730 liters
Water requirements by grass type:
| Grass Type | Weekly Water Need | Climate |
|---|---|---|
| Bermuda grass | 1.0–1.25 in (25–32 mm) | Warm / hot |
| Zoysia grass | 0.75–1.0 in (19–25 mm) | Warm |
| St. Augustine | 1.0–1.5 in (25–38 mm) | Warm, humid |
| Kentucky bluegrass | 1.0–1.5 in (25–38 mm) | Cool |
| Tall fescue | 1.0–1.25 in (25–32 mm) | Cool, adaptable |
| Fine fescue | 0.75–1.0 in (19–25 mm) | Cool, shade |
| Ryegrass | 1.0–1.5 in (25–38 mm) | Cool |
When to water:
- Early morning (6–10 AM) is ideal. Less evaporation, and the grass dries before nightfall.
- Evening watering leads to prolonged leaf wetness and promotes fungal disease.
- Avoid midday watering. Most of it evaporates before it reaches the roots.
Signs of underwatering:
- Grass blades fold or roll lengthwise
- Footprints remain visible after walking across the lawn
- Bluish-gray tinge instead of green
Signs of overwatering:
- Constantly soggy or spongy soil
- Fungal patches, mushrooms, or moss
- Thatch buildup
- Runoff flowing off the lawn
Deep and infrequent watering builds deep roots: Water deeply 2–3 times per week rather than a little every day. Deep roots make your lawn drought-resistant and less susceptible to heat stress. Aim for water to penetrate 6–8 inches (15–20 cm) into the soil.
Sprinkler output check: Place empty tuna cans on the lawn while running your sprinkler. When the cans hold 1 inch (25 mm) of water, you have watered the correct amount. Time how long that takes and you have your sprinkler’s output rate in inches per hour.
Rough figures if you would rather not measure: rotary and impact heads put out about 0.5 in/hr, fixed spray heads about 1.5 in/hr, and an oscillating hose sprinkler around 0.6 in/hr. Pick one in the sprinkler field above and the result panel works out the run time per session. The cans are still worth doing once, because head spacing and water pressure move these numbers a long way, and half the lawns that look “patchy” are simply getting uneven coverage.
A note on run times over half an hour: Soil only absorbs water so fast. Once a session runs past about 30 minutes on most soils, the surface starts to pond and the rest runs off into the street. The fix is cycle-and-soak: split the session into two or three shorter runs an hour apart. Clay soils need this the most, sandy soils rarely need it at all.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.