Learn How to Measure for Replacement Windows

So you’ve decided that it’s time to replace the old windows in your house with some shiny new windows that are energy-efficient and air-tight. You don’t want to waste any time so you’re going to measure for replacement windows yourself. No need to worry, it’s easy to learn how to measure for replacement windows.

What You’ll Need to Measure Windows for Replacement

Measuring a window doesn’t require any fancy tools or equipment. The only tools you’ll need to accurately measure your current windows are:

  • a measuring tape
  • a pad of paper or notebook
  • a pen or pencil for writing down measurements

That’s it! Are you ready to get started? Read on to learn exactly how to measure for replacement windows.

How to Measure for Replacement Windows – It’s Easy!

To accurately measure a window for replacement, you’ll need to find an accurate measurement of its height and width. Generally speaking, you won’t need a depth measurement in most cases unless the wall that will be accepting the new window is under 3″ deep. You’ll be measuring your windows from inside your home so don’t worry about having to climb over the bushes outside!

Measure the Width

Let’s start with the width measurement of the window first. We’re going to take at least 3 different width measurements at different points on your window. Take one width measurement at the very top of the window, one at the middle of the window and one at the bottom of the window.

Measure from the surface of the jambs of the window, not from the trim pieces or parting beads. Those will be taken off when the window is removed. If your window is exceptionally tall, take a few more width measurements just to be sure. Make certain that you are measuring to within an 1/8″ inch in your measurements.

Measuring Width of Window

Record each of your width measurements on paper. You might be wondering why you’ve taken at least 3 measurements of the width at 3 different points on the window. It’s because we are looking for the smallest of those measurements so that when you order a window, it will be sure to fit and not be too large for the actual size of the window opening. Circle your smallest width measurement.

Measure the Height

Measuring the height of a window for replacement is almost exactly the same as the width measurement. Measure the height from each side as well as the center of the window.

measuring the height of a window

Again, if you have a very wide window like a bay or bow window, then take more height measurements at different points of the window that are evenly spaced. Similar to the width measurement, you will want to ignore any trim and measure from jamb to jamb to get the most accurate height measurement of your window. Record your window’s height measurements on paper and circle the smallest one.

Checking That Your Window is Square

The last thing to check for is that your windows are square. Meaning that each corner of the window is 90 degrees and there is an equal length from corner to corner diagonally. Checking the squareness of your window will let the window installers know ahead of time if they will need to add shims or make adjustments to your rough window opening after taking out your old window.

You’re going to take two measurements from each corner diagonally across the window. So from the top-left corner of the window to the bottom-right corner and vice versa.

measure windows diagonally to tell if they are square

Take down your measurements and compare. If both of these measurements are within 1/4″ of each other, then you should be fine. Don’t worry if the difference is a little bit greater, during installation most window installers will be able to add wood shims to your window opening to make your window sit exactly square.

window measurement

Measuring an Architectural or Arch Top Window

Measuring a window that is curved or has a round top can be a little bit trickier to measure at first, but it is still relatively simple. There are many different variations of specialty windows but most have some sort of curvature that must be measured for replacement.

Start off by measuring the square part of the window first and excluding the arched portion of the window. Next, take a measurement from the lowest point of the window to the highest point of the arch. This will typically be in the exact center of the window. Again, remember to not take into account any trim pieces in your measurements.

Ordering Replacement Windows – DIY vs. Hiring a Window Company

Now that you know how to measure for replacement windows, all that’s left to decide is whether you are going to install the windows yourself or hire a window company to do it for you and provide them with your window measurements.

If you were to go the DIY window replacement route, keep in mind that there will be no one to back up your measurements, potentially leading to poorly sized windows that could be too large or too small for your window openings. Additionally, most major window manufacturers will not be able to offer you a warranty on the performance of the window since it was not professionally installed.

For most people, hiring a window installation company to do the work is the safest bet for several reasons. For one, you won’t have to worry about ordering windows. Another reason to go the professional route is that you won’t have to worry about any warranty issues since your new replacement windows will be installed by pros. Hiring professionals to install your windows will pay for itself and then some considering the lower energy costs and the increase in home value that new windows will bring. Get a free quote online for your replacement windows today!

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