How to Calculate Square Feet for Exterior Painting

Properly calculating square footage is an important step in many home remodeling jobs, such as exterior painting.
You need to know how to calculate the square footage in order to buy the right amount of exterior paint. Fortunately, it's not difficult. Anyone with a basic knowledge of simple mathematics and instructions can calculate square feet for exterior painting. Additionally, when you have mastered the concept of calculating square footage, you can use the same basic skill for several other household projects. .

Step 1

Walk around the perimeter of your house, sketching its outline. Your sketch does not need to be to scale, but make sure that you include all of the corners, so that every exterior wall surface is represented on the sketch. Your sketch does not need to include any features that will not be painted, but do note all dormers on your sketch.

Step 2

Measure all exterior walls horizontally (side to side) with a measuring tape or measuring wheel. Note the horizontal measurements on your sketch, with each measurement placed by the wall it represents.

Step 3

Measure all exterior walls vertically (top to bottom) from the bottom of the wall to the bottom of the roof line. Do not include any gables (the triangle shaped part of the wall under a pitched roof) yet. Note the vertical measurements of each exterior wall surface next to the horizontal measurements on your sketch.

Step 4

Determine the square footage of the major wall surfaces by multiplying the width of each wall by its height. Note all square footage calculations in a column on one side of your sketch to be added later.

Step 5

Determine the square footage of all gables. To determine the square footage of a gable, measure its height (from the bottom of the gable to the top of the gable) and its width (usually the width will be the same as the side of the house the gable is on). Multiply the height and the width and divide the result by 2. Note the square footage of all gables in your column of square footage.

Step 6

Measure the square footage of all dormers in the same way as you have already done for other exterior walls and note the results in your square footage column.

Step 7

Add all square footage in your square footage column. The resulting total is the total square footage for exterior painting.

Things You Will Need

  • Measuring tape or measuring wheel
  • Paper
  • Pencil
  • Calculator (optional)


  • Do not subtract surfaces such as doors and windows from the square footage of your home when determining how much paint to purchase. It's better to overestimate a little than to underestimate.
  • If you have horizontal siding, you can calculate the height of your home more easily by measuring one strip of siding or clapboard, counting the strips of siding and multiplying the width of the siding strip by the number of strips. Consider using an online calculator such as the one at servicemagic.com to save some arithmetic.

About the Author

Dell Markey is a full-time journalist. When he isn't writing business spotlights for local community papers, he writes and has owned and operated a small business.