Window Basics – Part 3 (By Chad Vankoughnett)

How To Measure Your Windows For Replacement



When replacing your windows, it is very important to get accurate measurements of the opening so that the new windows will fit in the existing hole (unless you are wanting to do a considerable amount of renovation work to make the hole bigger). Windows are a large investment, and are usually made to order, so if you aren’t confident that you can get the measurements accurately, it is far better to have a professional measure your opening.

Let’s assume you are confident that you can get the job done right. There are several ways to measure windows – from the inside, the outside, the rough opening, etc. We are going to assume that you are replacing windows that already exist in the home. In that case, we will give you two options for measurements. The first is from the inside, the second from the outside. Ideally, we would like to receive both measurements unless we will be doing the installation.

When measuring from the inside, use a tape measure to determine the width of the window from the INSIDE of the window sill. Measure the opening at the top, the middle, and the bottom, and write down the SMALLEST measurement you get. Remember, if your window is too large, it won’t fit in the opening. Do the same with the height, measuring the middle and along each side, and write down the smallest number.

When measuring from the outside, you will want to measure the dimensions from the OUTSIDE of the brick moulding. That is the trim that goes around the outside of the window. Again, measure in three places, and provide the smallest number. You will also need to provide us with the jamb width. Windows come standard at 4 ½” to 6 ½” depending the wall thickness. This is standard because the wall frame is usually built from either 2×4 or 2×6 lumber. Then add the drywall which is ½” and the sheathing on the exterior, which is also ½”. If you have an older home, or if you have done renovations on the wall, this number might be different. Simply measure the distance from the outside of the sheathing to the inside of the drywall in the window opening. This can be a bit tricky if the window is still in place, so don’t be afraid to call for help in determining this number.

That’s all there is to it. Take your time, measure everything a couple of times to be certain, and be as accurate as you can. As stated earlier, if you are uncertain at all about getting a correct measurement, please give us a call. We would be happy to have someone come to your home and do the measurements for you.

– Chad Vankoughnett