How to Calculate Lawn Irrigation Water Usage and Costs

By: Ben Erickson

Sprinkler watering lawn

With drought gripping much of the country, and the price of water on the rise, it’s become increasingly important to know how much water you use to irrigate your yard as well as how much it costs.

Watering Do’s and Don’ts

Water your yard early in the morning and soak the ground thoroughly so that it penetrates to a depth of at least 3″. While the amount of water needed will vary depending on your climate, the weather, and the time of year; the general rule of thumb is to make sure your lawn receives 1″ of water to your lawn per week during dry conditions.

To see how much water your grass is actually receiving, put several containers with straight sides—such as a coffee mug, metal can, or plastic container—on the ground around the yard while you are watering. Then use a ruler to measure the depth of the water in the container.

Measuring water in a cup

Calculating Water Use

To provide your lawn with one inch of water takes a little over half a gallon per square foot (0.623 gallon to be more exact). That means that every 10’x10’ area will require over 62 gallons of water. That doesn’t sound like much until you consider that a 100’ x 100’ lawn uses 6,230 gallons of water every time you turn on the sprinklers!

To calculate the amount of water you use, multiply the width times the length of your yard in feet to get the number of square feet of area. Then multiply that figure by 0.623 to come up with the number of gallons used (or use our calculator below).

This assumes that your yard is square or rectangular. For more unusual shapes, you’ll have to dig out your old high school geometry book to come up with the amount of area involved.

lawn sprinkler

Calculating Water Costs

Now that you know how much water you’re using, you can estimate how much it will cost to keep your lawn green. While city water systems usually give separate prices for water and sewer services on your bill, in most cases both are actually based on the number of gallons of water you use.

So for every 1,000 gallons of water that comes out of your faucet, you are also charged not only for the water but for 1,000 gallons of sewerage. This holds true regardless of whether it goes down the drain or on your grass.

Many cities will install a separate meter for irrigation purposes that does not include the cost of sewerage. This can save a lot of money, though you will have to pay several hundred dollars to have it hooked up as well as a monthly minimum whether you use it or not.

To calculate the cost of watering your yard, divide the number of gallons used by 1,000 then multiply by the price you pay per 1,000 gallons (see our calculator below). Don’t forget to include the sewer costs unless you have a separate meter.

Lawn sprinkler

Here in Mobile, Alabama, it costs $2.00 per 1,000 gallons for water plus $4.26 per 1,000 gallons for sewer, for a total of $6.26 for every 1,000 gallons of water that comes out of the tap. That means that to supply a 100’ x 100’ yard with one inch of water costs over $12.00 if you have a separate meter for irrigation, or $39.00 if you don’t. If you water your yard every week during the summer, the cost will add up to close to $50 or $156 a month.

Given the severity of the current drought, water rationing is already taking place in some parts of the country. When supplies run short, lawn irrigation is the first thing to go. If you find the cost of watering your yard too steep—either financially or ecologically—you might consider getting rid of grass altogether and planting drought resistant shrubs and other plants instead. Not only will it help conserve water and save money, but you won’t spend your Saturdays behind the lawn mower either.


Lawn Irrigation Costs Calculator
Length of yard in feet
Width of yard in feet
$

Cost per 1,000 gallons of water
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17 Comments on “How to Calculate Lawn Irrigation Water Usage and Costs”

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  • Steven E Tesenair Says:
    August 3rd, 2016 at 11:51 pm

    I’ve come up with some numbers and they are pretty high when I did the math for my yard. I’d like to consider myself fairly competent in the turf field and I do quite well with my yard. I am trying to figure how much time is required to apply 1 acre inch in my front yard and the numbers I’ve come up with are astonishing. I’ve figured 26 hrs with 1 3gpm sprinkler attached to a hose on .172 acres.
    Here is my math using your formula….
    43,560 x .172 = 7492 Sq ft
    7492 x .623 = 4668gal
    4668g ÷ 3 gpm = 1555min ÷ 60 = 25.9 hrs.
    Correct me if I’m wrong, but……WOW!

    Here is the method I used before…
    1 acre in of water = 27,000gal
    Cross multiply and we get
    27,000gal = 1 acre inch
    X = .172 acres inch
    27Kg x .172 = 1X
    4644gal of water to get an inch of water for my front yard of 7492 Sq ft.
    At 3 gpm that would give me 1548 min. and again around 25 hrs.
    Somewhere on found a formula for precipitation rates to figure inches/hr for square spacing.
    (GPM x 96.25) ÷ spacing
    So here’s what I came up with. My sprinkler throws approx 30 ft at 3gpm.
    (3 x 96.25) ÷ 30 (30)
    288.75 ÷ 900
    = .32in/hr
    So in approximately 3 hrs per spot I can put out 1 in of water and I have anywhere from 10 to 11 placements. I’m not sure how or why I got off on this tangent but it’s mind-boggling when you sit down and do the math on all this and how much it all costs. I just need to go ahead and finish installing my irrigation system I designed last summer.



  • Madison Says:
    January 24th, 2016 at 4:57 pm

    I share a well with my neighbor to irrigate my lawn. I want to pay my share of the electric costs. The sprinkler system runs about six hours a week. How do I calculate the cost?



  • Rick Thomson Says:
    August 28th, 2015 at 12:44 pm

    I have had absolutely no luck finding a plumber or other contractor who will do a tap and install an irrigation meter for my sprinkler system. I need this or my municipality will charge for water & sewer for this system-even though the irrigation water is obviously not going down the sewer. Is the installation of these meters typically done by a plumber? The company who installed the system does not install meters and I can’t find one who will. Any ideas? I have to buy the meter from the municipality but they also do not install.



  • Rayyan Says:
    November 12th, 2014 at 8:52 am

    how to calculate water requirement for a foot ball ground per hour per day per week



  • Matt Says:
    May 16th, 2014 at 12:23 pm

    Does anyone have an opinion on drip irrigation for lawns? I watched a video on a new drip line developed by Rainbird which is installed under the turf. My lawn takes a lot of water so I’m looking into alternatives. Any opinions would be appreciated.



  • Beth Says:
    May 2nd, 2014 at 3:10 pm

    How much more water per square foot does St Augustine require than Bermuda or Zoiysa?

    Thanks!


  • Official Comment:


    Ben Erickson Says:
    November 2nd, 2013 at 8:42 am

    Don,
    Glad to hear our irrigation calculator was on help!



  • Don Mitchell Says:
    November 1st, 2013 at 5:54 pm

    very sound information, trying to figure cost to haul water from river to water yard two times a week. It will save me some money. thanks.



  • angelshine Says:
    October 19th, 2012 at 10:11 am

    this helped alot fr my school. thx!!



  • dee Says:
    June 11th, 2012 at 8:51 am

    water usage info very helpfull. Can you tell me the cost of running the well pump per hour. I use mine for approx 8 hrs per week for 3/4 of an acre. Is this too nuch?



  • jamil Says:
    March 10th, 2012 at 12:45 am

    how tocalculation water consumption by irrigation system to find the exactely pump for irrigate the plants only 16 hours daily ?



  • arkie Says:
    June 28th, 2011 at 8:50 am

    I have 3 different area 25′ wide x 100′ long. I need to water these areas from the 25′ side. Using 120* sprinklers, that will water the full 25′. I can use 3 different pipes 3/4″ are 1″ pvc, each for 1 area. I have a well for this use and figure on watering 1 area at a time. With a psi of 50to60 psi.
    Can you advise me?
    Thanks
    Arkie
    western arkansas



  • Rainwater Collection Systems - Greener People Says:
    May 11th, 2010 at 12:35 pm

    […] 2000 sq ft of garden * 0.623 gallons (equivalent of 1 inch of rain) = 1246 gallons per watering (DIY: Calculating Lawn Irrigation Costs – Danny Lipford) During the summer months we get 3.5-3.8 inches of rain. So I'm thinking about 2,000-3,000 gallons […]



  • Carlos Says:
    July 6th, 2009 at 7:59 am

    Your website sure is loaded with valuable information….very easy to read and nicely colored….maybe some flowers of the month will be nice to see
    thanks
    I’ll be back & tell my friends about you
    Happy Summer
    Carlos



  • Calcuate the Cost of Watering your Lawn-Calculator - Raleigh, Durham, Chapel Hill, Cary - North Carolina (NC) - The Triangle Area - City-Data Forum Says:
    May 16th, 2009 at 1:10 pm

    […] the Cost of Watering your Lawn-Calculator DIY: Calculating Lawn Irrigation Costs – Danny Lipford I found the above website so helpful in helping us to know what actually we might spend on […]



  • Craig Borglum Says:
    March 3rd, 2008 at 7:12 pm

    I like the calculator. It is a good starting point for saving water. Unfortunately without calculating how even the water is distributed,
    the equation will be off the mark.

    Certified Landscape Irrigation Auditors use a complicated mathematical formula to determine the “Distribution Uniformity Lowest Quarter”.

    Copy and paste DUlq into Google and a more detailed explanation can be had.

    In essence, the amount of water necessary to supply the driest is 25% of the yard needs to be factored in. 100% distribution uniformity is impossible.

    This is why proper irrigation design is so important.

    If a system is only 45% efficient (very common) 55% of the water will be wasted trying to supply enough water to the “lowest quarter.”

    The “throw water in the air” sprinkler system design approach favored by uneducated “irrigation designers” will soon come to an end.

    Thank goodness. None us us can afford those guys anymore.



  • Dog Crazy Says:
    October 20th, 2007 at 4:08 pm

    Thank you! That was a great help.
    ~DogCrazy


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