How To Measure the Area (square footage) Of Your Lawn.

   I wrote this page because people often have trouble figuring out the area of their lawns. It's a lot easier than you might think. Even the most complicated lawns can be broken down into smaller areas that are easy to measure. I'm going to use the following example to show how the area of any lawn can easily be measured by breaking it into rectangles, trapezoids, triangles and circles.

   The lawn I planted the other day was an "L" shaped front yard on a corner house. The homeowner didn't know how to figure out the square footage.

• The front part of the lawn was a rectangle. It measured 83' by 27' (2,241 s/f). On the right side of the lawn, the sidewalk going to the porch took a 4' by 21' rectangle (84 s/f) out of the lawn area. Rectangles are measured by multiplying length times width. The front part of this lawn was 2,220 s/f.
   
• The left side of the lawn area wrapped around the side of the house. Quite often lawns that appear rectangular are actually trapezoidal. But that's OK, trapezoids are almost as easy as rectangles.
   
  This side lawn was a trapezoid. It was 25' wide where it connected to the front lawn. But it was 27' deep at the sidewalk and only 23' deep against the house. Trapezoids are measured by averaging the eneven depth and multiplying it times the width. 27' added to 23' equaled 50'. When I divided 50' by 2, I discovered that the area of that side of the lawn was the same as 25' by 25'. That made the "L" part of this lawn 600 s/f.
   
• At the front left on the outside corner of the lawn area, the sidewalk removed a quarter circle from the lawn area, with a radius of 8'. (Just for reference, the radius of a circle is half of the diameter, so in this case the diameter was 16'.)
   
  The area of a circle can be figured by multiplying 3.14 (pi) by the square of the radius of the circle. I got the square of the radius by multiplying 8' x 8' to get 64 s/f. I multiplied that by 3.14 (pi) to discover a circle with an 8' radius has an area of 200.96 s/f. Therefore a quarter circle with a radius of 8' would be 50 s/f.
   
  The effect the corner sidewalk had on the lawn area is the same as removing an 8' by 8' square (64 s/f), and replacing it with an 8' quarter circle (50 s/f). The sidewalk removes 16 s/f from the area of this lawn. Whew!
   
  
• Because this house had a 3 car garage and a 2 car driveway, there was a 16' wide by 24' deep triangle of lawn area next to the driveway. Triangles are really easy to measure. If two of the legs of a triangle form a 90 degree angle, simply multiply the length by the width and divide the result by two. This lawn was 16 times 24 equals 384, divided by 2 equals 192 s/f.
   
  Even if two of the legs of a triangle don't form a right angle, it would still easy to measure (but hard to describe). Let's say the three legs measure 20', 14' and 16'. Simply divide it into 2 smaller right triangles. I came up with an 11' by 8-1/2' by 14' triangle (11' x 8.5' = 93.5 s/f / 2 = 46.75 s/f) and an 11' by 11-1/2 by 16' (11' x 11.5' = 126.5 s/f / 2 = 63.25 s/f) triangle. In other words, I just broke it into two right triangles on the longest leg, measured each seprately, and added the results to discover this example is about 110 s/f.
   
  Triangles are a good example of when fuzzy math is more appropriate than trying to be dead accurate. That 11' distance I got was really a couple of inches over 11', but I chose to ignore it. And instead of actually triangulating the 90 degree angle I eyeballed it. What I'm trying to say is that when measuring lawn area it's not always necessary to be dead on accurate - sometimes real close is good enough.
   
  

   You should know that more often than not, houses are not square to streets, driveways, property lines or anything else. But instead of going into that here, I'll refer you to the Measure Your Yard section of Jess Stryker'sSprinkler Design Tutorial.

   I plan to put drawings and visual aids on this page. (And perhaps, with your help, find better ways to explain my examples.) I put this page up a little prematurely because people kept calling to tell me the link to it didn't work on the new "Index Page" I just posted. Feel free to E-mail suggestions for making it better.

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