Lawn Irrigation Calculator
Calculate weekly water need, gallons per session, and minutes per zone for a lawn sprinkler schedule. Adjusts for soil type, climate zone, and the 0.623 gal per sq ft per inch formula, and warns when one session is longer than the soil can absorb.
Water Needed for a 1,000 sq ft Lawn
| Weekly water depth | Gallons needed | Total weekly runtime at 30 GPM |
|---|---|---|
| 0.5 in | 312 gal | 10.4 min |
| 1 in | 623 gal | 20.8 min |
| 1.5 in | 935 gal | 31.2 min |
| 0.75 in | 467 gal | 15.6 min |
| 2 in | 1,246 gal | 41.5 min |
Frequently Asked Questions about the Lawn Irrigation Calculator
How much water does a lawn need per week?
Standard cool-season turfgrass needs about 1 inch of water per week, including rainfall, to stay green and grow a deep root system. Warm-season grasses like Bermuda or Zoysia get by on slightly less, while newly seeded or sodded lawns need more frequent light watering until roots establish. The calculator uses 1 inch as the default and lets you bump it up for stress periods or down if your turf species needs less.
Why does soil type change how long I can run sprinklers?
The calculator uses 60, 45, and 25 minutes as planning caps for sandy soil, loam, and clay. Actual infiltration also depends on compaction, slope, thatch, sprinkler precipitation rate, and recent rain. Use catch-cup tests and observe runoff on the site. Split a run into shorter cycles when water begins to pool or flow away.
Where does the 0.623 gallons per square foot per inch number come from?
It is a unit conversion. One cubic foot is 1,728 cubic inches, and one US gallon is 231 cubic inches, so one cubic foot holds 7.4805 gallons. One square foot covered by one inch of water is one-twelfth of a cubic foot, or 7.4805 divided by 12, which equals about 0.6234 gallons (rounded to 0.623). Multiply lawn area in square feet by inches of water by 0.623 and you get gallons needed.
When is the best time of day to water a lawn?
Early morning is often a practical watering window when local restrictions allow it. Wind, heat, humidity, disease pressure, and irrigation rules vary by location. Avoid schedules that create runoff or leave foliage wet for long periods, and use your local extension service or water utility for seasonal guidance.
Why are two deep waterings better than seven shallow ones?
Where the soil can absorb water without runoff, less frequent and deeper watering can encourage deeper rooting than frequent shallow watering. The right duration and frequency still depend on grass species, soil, weather, irrigation rate, local restrictions, and new-plant establishment needs. Adjust from observed soil moisture instead of assuming a fixed weekly pattern.
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