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How to Calculate Rough Siding Footage

How to calculate your exterior siding footage

If you’d like to estimate how much it will cost to have siding installed on your house, you must figure your exterior square footage and then multiply that number by the siding cost per square foot Here are a couple of ways to accomplish this.

Rough estimate:

  1. Know your interior square footage.
  2. Add any extra footage added on to your house(i.e. garage space).
  3. You now have a very general idea of your exterior siding footage!

Please remember that this method should never be used when actually making important buying decisions, but if all you’re looking for is a quick ballpark number, it will do. Basically, the principle is that your interior square footage is equal to your exterior square footage. It is likely to vary within 200 square feet and in some cases as much as 500 square feet. This method also does not take into account spaces like windows and doors that will not be covered with siding. Keep reading if you need something more specific.


How to Calculate Exact Siding Footage


Exact calculation:

This is your chance to brush up on your geometry. No, really it’s not hard. You’ll need paper, a tape measure, a calculator, and a pencil. And here’s a tip: round off amounts to the nearest whole or half so it doesn’t get too confusing. That will get you close enough, especially since you’re just using the measurements to figure siding costs.

First of all, you need to know the two basic shapes found on the exterior of a house and how to figure the area for them:


 Siding Material Area for a Rectangle

The area, A, of any type of rectangle can be found by multiplying the lengths of the two sides.


 Siding Material Area for a TriangleA=1/2bh

  1. Make a little drawing of each side of your house. Draw in the triangles and rectangles the make up each side. Remember, count only the parts that will receive siding.
  2. Go outside and actually measure those parts of your house, writing the measurements down on your drawing.
  3. Figure the area of each part, using the area formulas above for rectangles and triangles.
  4. Add together all the area measurements that you figured in step 3.
  5. Measure and find the areas of any doors and windows or any other places that will not be covered by siding.
  6. Add the areas from step 6 together to find the total square footage not covered by siding and subtract this number from the total in step 4.
  7. Finally, multiply the exterior square footage of your house by the cost of siding per square foot. (ex. $4.60 x 2500 = $11,500) This is your estimated siding cost.

Please remember that extras such as soffit, fascia, and anything customized will cost more. The above method will give you an approximate figure that may be lower than the actual estimate your siding manufacturer will give, but it would be virtually impossible to help everyone find the exact cost of siding for their unique house without extensive instructions.

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