Darden Building Materials

Your windows can last 20 to 25 years (or even longer if you maintain them), so, odds are, you’ve never had to worry about replacing them. If your windows are reaching old age, you might be wondering the right way to find new ones.  

It all starts with measuring.  

We’ve put together this guide to show you how to measure for replacement windows, so make sure you keep reading below! 

Make Sure You Have the Right Tools  

You don’t need much to measure your windows, but you should make sure you have everything on hand before you start. Trying to remember the measurements in your head so you can write them down later is a bad idea, no matter how good your memory is. Buying replacement windows that are too big or too small is an expensive mistake.  

Here’s what you’ll need: 

  • Tape measure (or slide ruler)  
  • Pen and Paper for notes and measurements
  • Step ladder (if your windows are tall)

A slide ruler tends to be more accurate than a measuring tape, so it will do the job better. However, if you only have a measuring tape, it should work just fine.  

Measuring Your Windows 

Don’t rush the process when measuring your windows. You want to make sure the measurements are as accurate as possible, so go slow and have patience.  

You’ll need to measure these three spots (if your windows are oddly shaped, you may need to take more).  


Start by measuring the width of your window at the top. Write down the number you get on your paper then measure the width again in the middle and at the bottom of your window. 

Don’t be surprised if all three numbers are different. Over time, weather and moisture can make the window frame warp, shrink, or expand in some places. 

Use the smallest number as the rough width of your window.  


Repeat the same measuring process with the length of your window. Take at least three different measurements and use the smallest number as the rough opening.  


To find the depth of your window, open the glass and measure from the outside of your window frame to the inside of your window frame. Do this at least once on both sides of your window and the top and bottom. Again, use the smallest number you get.  

Re-Check All Your Measurements Again  

After you finish measuring your window, do it all again. Measure twice, cut once is a popular expression that comes to mind. You should re-check your measurements at least two to three times to make sure they’re correct. The last thing you want to do is buy replacement windows that don’t fit in your home.  

How to Measure for Replacement Windows  

Figuring out what size replacement windows you need for your home does take some time, but it isn’t hard. If you follow the tips on this guide, you’ll learn how to measure for replacement windows and get accurate numbers.  

Not sure where to buy new windows now that you’re ready? 

Make sure you check out some of the options in our store!