How to Measure for Siding Step-by-Step

It’s a good idea to start the process by sketching the exterior of your home. Start with the front and draw a rough sketch of all of the faces you plan to cover with siding. Be sure to include faces on doghouse dormers and other bump-outs. Label each face with a number on the sketch, and then make a list of each number below the drawing. Be sure to exclude the faces you won’t be refinishing if you’re doing a partial siding replacement.

Next, head to the sides and rear of your home and repeat the process. By the end, you should have a complete list of every surface you plan on siding.

Use your sketch to section off portions of the faces of your home. The easiest way to do this is to break down the faces into simple geometric shapes. For example, homes with gable roofs have pentagonal sides. Section these off in your sketch into a rectangle for the bottom portion and a triangle above it. More irregular shapes may require that you break up each face even further.

Next, get your ladder and tape measure and begin working through your list of faces that will get new siding. Your goal is to measure and record the square footage of each face you marked down in the previous steps. You can use the strategies below to get accurate area measurements. If your numbers are in non-whole feet, you can round up to the nearest half-foot.

• For rectangular areas, take the measurements in feet and multiply the length by the width.

• For triangular areas, measure the base and the height in feet. Multiply them together, and then divide by 2.

• For areas with round edges, measure them as if they were rectangular. Take the height at the highest point and the width at the widest point in feet and multiply them together.

Now, you’ll need to measure wall openings, like doors and windows, on each face of your home. Take the measurements in feet, rounded down to the nearest half-foot, and multiply them together. For round windows or arched doorways, you can take length and width measurements at the tallest or widest parts and multiply.

You should now have a comprehensive list of measurements for all areas of your home that you need to install siding over. Add up all of the areas you calculated in step 3 (the complete faces) and subtract all of the areas you calculated in step four (the wall openings that don’t need siding). This will give you the actual square footage of siding you need, not accounting for waste.

In all cases, your siding installer—which could be you if you’re DIYing siding installation—will do what they can to make the most of the siding material they purchase for your project. However, there will be areas they’ll need to cut off that are too small to use elsewhere. To ensure you have enough material to cover your home, add 10% to the figure you calculated in step five. This will give you your total siding area plus extra to account for mistakes and wasted material.