How to Figure Square Footage for Vinyl Siding

I know this sounds easy for some people, but for others, it seems to be a very difficult task. It is for these people that I am writing this. If you are trying to figure out how to measure, calculate, and purchase vinyl siding, just follow these rules and you won’t go wrong. First, you need to know what kind of siding you are going to purchase. This is very important. Some siding is eight inches, and other siding may be nine or ten inches. If you already know what style you are going to use, then you are ready.

It is a good idea to draw a picture of your house, at least the perimeter. It doesn’t have to be a work of art, it’s just for reference, and to double check yourself. (I live by the rule “measure twice, cut once”) Now you need to start measuring. Measure across the wall, (round up to the next foot) and write this on the diagram that you have. Next, measure the height of the wall, and write this down. The formula is: (Width X height = square feet). This is why it is important to know the style. ( If the wall measures eight feet and three inches,and you are using eight inch siding, you need to allow for five inches of waste at the top.) I usually round up one foot. You can usually take back what you don’t use, but ask first. You don’t want to pay for siding that you won’t use. It is a good idea to keep a couple of pieces just in case you need to repair something later.

Now you need to deduct from the total square footage, for windows and doors. The formula is the same, Width X height. The remainder is the square footage of the wall. Do this for all walls on the house. Now you need to figure the gables of the house. This is the triangle of the house next to the roof. Measure this triangle, and the formula changes at this point. The new formula is (Height X ½ Width + twenty percent. (the twenty percent allows for waste). Write these measurements down on the diagram, and add all of the square footage together. This gives you the total square footage of the house. One square of siding is one hundred square feet.

To figure your accessories, you can just count most of them. If you have four corners on your house, you need four corner posts, unless it is a two story house then it doubles. These posts are ten feet long. If you have any inside corners, count them for inside corner posts. For each window or door, usually you need two pieces of J-channel unless they are very large. You have to measure everything else. The J-channel is twelve feet long, so take the measurements and divide by twelve. For your starter strip, you need to add the perimeter measurements together, and this will give you the total footage you need. The starter strip is either ten or twelve feet long. As I said, Double check everything, and that’s all there is to it.

As a thirty year installer/carpenter, this has always worked for me and it will work for you as well. Good luck with the installation, but that’s another article altogether.