Lawn Watering Calculator
Enter your lawn size and the weekly depth of water it needs, and this tool multiplies them by 0.623 gallons per square foot inch to show total gallons per week. Add a sprinkler flow rate and it divides that volume by the flow to estimate how many minutes to run the sprinkler. A 1,000 square foot lawn at one inch per week works out to 623 gallons, or about 124.6 minutes with a 5 gpm sprinkler.
How to estimate lawn watering
- Type your lawn area into the Lawn area field, measured in square feet.
- Set Water per week to the depth your grass needs, in inches (one inch is a common starting point).
- Enter your Sprinkler rate in gallons per minute, or leave it at zero to skip run time.
- Read the Water per week gallons and Sprinkler run time in the result cards.
- Press Copy estimate to save the gallons and run time as text.
Examples
1,000 sq ft lawn at one inch per week
Lawn area 1000 sq ft, Water per week 1 in, Sprinkler rate 5 gpm
623 gal per week, sprinkler run time 124.6 min
Larger lawn in a dry spell
Lawn area 5000 sq ft, Water per week 1.5 in, Sprinkler rate 10 gpm
4672.5 gal per week, sprinkler run time 467.25 min
Volume only, no sprinkler rate
Lawn area 2500 sq ft, Water per week 0.75 in, Sprinkler rate 0
1168.13 gal per week, run time shows add a rate
Frequently asked questions
How much water does a lawn need each week?
Most cool and warm season lawns want about one inch of water per week, rain included. In heat or drought some grasses climb toward one and a half inches, while spring and fall usually need less. Set the Water per week field to match your grass and climate.
Where does the 0.623 gallons figure come from?
One inch of water spread over one square foot is one twelfth of a cubic foot, and a cubic foot holds roughly 7.48 US gallons. Dividing 7.48 by 12 gives about 0.623 gallons, the constant the tool multiplies area and depth by.
How is the sprinkler run time calculated?
It divides the weekly gallons by your sprinkler flow in gallons per minute. So 623 gallons at 5 gpm is about 124.6 minutes for the whole week. That is total run time, which you would normally split across two or three watering days.
How do I find my sprinkler's gallons per minute?
Set an empty container under the sprinkler, run it for a set number of minutes, then divide the gallons collected by the minutes. Product spec sheets and hose bib flow tests also list a flow rate you can enter.
What if I leave the sprinkler rate at zero?
The tool still shows the weekly gallons, but the run time card reads add a rate because it has no flow to divide by. Enter any flow greater than zero to get minutes.
Should I subtract rainfall from the target?
Yes. Rain counts toward the weekly inch, so a rain gauge tells you the shortfall to make up. After a heavy storm you can skip a cycle to avoid runoff and waste.
Does this account for evaporation, soil type or slope?
No. The math is a straight volume estimate and does not model runoff on clay, fast drainage on sand, wind, or midday evaporation. Water in the early morning and watch for pooling to keep more of the water in the root zone.
Is it better to water deeply and less often?
For most lawns, yes. Fewer, longer sessions push water deeper and encourage roots to follow, which builds drought tolerance. Very sandy soils are the exception and may need shorter, more frequent watering.
Is my data private?
Yes. Every calculation runs locally in your browser with no numbers sent to a server, so your lawn size and watering habits stay on your device.
Learn more
- How to water your lawn deeply and less often
Turn a weekly water target into a deep watering schedule that builds stronger roots and wastes less water at the tap.
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