Home › Lawn & Garden Watering Calculator
Lawn & Garden Watering Calculator
Calculate how many gallons and how many sprinkler minutes you need to give a lawn or garden bed the right depth of water each week, and what it costs.
How to use it
- Enter the area you are watering in square feet.
- Most lawns and vegetable beds need about 1 inch of water a week including rain; hot, windy or sandy sites need more.
- Subtract the rain you have had (a rain gauge or tuna can works).
- Enter your sprinkler flow in gallons per minute (time a bucket) and the area it covers per setting.
How it works
One inch of water over one square foot is 0.623 gallons. Gallons needed = area × (inches needed − rain) × 0.623. Watering minutes = gallons ÷ flow (gal/min). Water deeply and less often - two or three longer sessions a week - to encourage deep roots, and water early in the morning to limit evaporation and disease.
Your actual need depends on soil, sun, wind and plant type; use the tuna-can test (an inch of water in a can) to check what your sprinkler really delivers in a given time.
FAQ
How many gallons of water per square foot per week?
One inch of water equals about 0.62 gallons per square foot, so a typical 1 inch weekly watering needs about 0.62 gallons per ft², or 620 gallons per 1,000 ft².
How long should I run my sprinkler?
Divide the gallons you need by the sprinkler flow in gallons per minute, then split it across the sprinkler settings needed to cover the whole area.
Does rain count?
Yes. Subtract measured rainfall from the weekly target; 1/4 inch or less barely wets the root zone, so do not count light showers fully.
Related calculators
Free calculator by FrostWise