How to Calculate Irregular Lot Size


The typical city homeowner's lot is 55 feet wide and 110 feet deep--6,050 square feet--or close to one-seventh of an acre. Every once in a while, however, you'll find lots situated in the corner of a subdivision or otherwise strangely shaped. Measuring the size of these irregular lots is a challenge because there is no standard formula for calculating their areas; they're not shaped like rectangles or any other standard polygons. The solution: Subdivide the strangely shaped lot into familiar shapes for which we do have standard formulas to calculate area.

Step 1

Acquire a visual of your land plot. Your municipality's Property Appraisal Division will usually provide maps that can be cross-referenced by parcel number, owner's name or site address. These maps may be available online or you might have to pick them up in person.

Step 2

Draw a dot at every angle or corner in the plot lines that define your lot.

Step 3

Use a ruler and pen or pencil to superimpose a series of rectangles over the map of your plot. Designate the longest edge of the plot--a vertical or horizontal line--as your orientation line. For any plot line that isn't perfectly parallel or perpendicular to this orientation line, encase that diagonal line in a rectangle--the dots at the end of that slanted line will represent opposite corners of the rectangle.

Step 4

Continue drawing rectangles around diagonal lines. Once all the diagonal lines have been encased by rectangles--which are half in, half out of your land plot--the only blank space left in your land plot should be regular rectangles with sides parallel or perpendicular to your orientation line. Draw lines to define these rectangles as well.

Step 5

Use a ruler to measure the length and width of each rectangle. For rectangles that are completely contained inside the land plot and don't overlap its edges at all, just multiply the rectangle's length by its width and note this in a column of numbers labeled "AREA." For rectangles on diagonal lines--the rectangles that are half in, half out of the plot--multiply length by width, then divide by two, and write the result in your "AREA" column. Do this for every single rectangle you drew; make a check mark in each rectangle as you compute its area to make sure you don't miss any.

Step 6

Add the numbers in your "AREA" column together. Finally, multiply this sum by the scale for the map you used as your reference; in other words, if every inch on the map represents 100 feet, you would multiply a measurement in inches by 100 to get the measurement in feet. The final result is the area of your irregularly sized and shaped lot.

Things You'll Need

  • Map of land plot


  • Demesne: Measuring Square Footage
Keywords: area of odd-shaped lot, irregular lot size calculation, corner lot square footage

About this Author

Marie Mulrooney has written professionally since 2001. Her diverse background includes numerous outdoor pursuits, personal training and linguistics. She studied mathematics at the University of Alaska Anchorage and contributes regularly to various online publications. Print publication credits include national magazines, poetry awards and long-lived columns about local outdoor adventures.

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