How To Measure Windows for Replacement

man holding home window frame to be installed

Did you know that getting a window replacement for your home can save you up to $465 per year on energy savings?

Replacing your home's old windows is a great way to save money over time while also boosting your home's value and curb appeal. While window installation companies know how to measure for replacement windows, you can save yourself a great deal of money by doing it yourself.

Learning how to measure windows isn't difficult but, if you're going to do it right, then you'll need to be precise in your measurements. Not only that but by measuring your windows yourself you'll knock hundreds of dollars off of the window replacement cost.

Continue reading to learn more about how to measure window size for your home's replacement windows.

How To Measure Windows

While getting accurate measurements for your window replacement is a vital step in the process, there are other important considerations that you need to make before you being replacing your windows.

Before you begin measuring your windows, be sure to thoroughly check the window frames to confirm that they're still in good shape. The wood frame needs to be in good shape because it is what supports your replacement windows.

If the window frame has sustained water damage or has started rotting then it won't be able to adequately support the windows that you're wanting to install on your home. If the frame is in good condition and is "in square" then you are good to start taking window measurements.

1. Write Down Your Measurements

The most important thing when measuring your windows for replacement windows is the accuracy of your measurements. Writing down the right measurements will save you time and money because you'll get the right windows the first time.

It doesn't matter if you're only replacing one window in your home or if you're replacing every window. You need to properly record the measurements of each window as you measure them.

There are documents like window measurement sheets that can help with the process of measuring your windows and keeping your recorded data safe. You can also record your measurements in a notebook or on a computer depending on your personal preferences.

If you're planning on replacing multiple windows then be sure to specifically label each of your windows. Labeling them like "Master Bedroom North Window" will help you keep your measurements straight.

2. Check For Square

You'll be able to determine if your window is in square after the completion of your first measurement of it. A window being in square means that every corner is still at a 90-degree angle. 

Making sure that the window is in square is important because if you get a window replacement and the window isn't square the replacement window will not open properly.

The best way to measure the window is by using a tape measure. Keep the tape measure taut and measure diagonally from the inside of the top left corner down to the inside of the bottom right corner and record that measurement.

Once you've done that, repeat it by measuring from the inside top right corner down to the inside bottom left corner and write that measurement down as well. 

If you check your measurements and they're within 1/4 of an inch of each other then your window frame is in good condition for a replacement window. If the difference is greater than 1/4 of an inch your best bet will be a new construction window.

3. Measure Window Width

When you measure the window's width, you'll measure it at three different spots. You'll want to measure at the bottom, the middle, and the top of the window.

The best way to measure your windows for width is to take the tape measure and measure against the jamb on each side of the window. The jamb is the part of the window that is the vertical board on which the window slides when you open or close it.

The best way to measure the bottom of the window is to slide the window up and measure from one jamb across to the other at the lowest point of the window. 

For measuring the middle portion of the window, you'll want to slide the window completely open and measure from one jamb to the other at a point that is as close to the middle as you can get.

Measuring the top of the window involves closing the window and measuring the window from jamb to jamb at the highest point that you can reach.

After each measurement that you take, be sure to record your findings. If there is a shortest measurement, be sure to highlight it so that you're aware of it.

4. Measuring the Height of the Window

The process of measuring your window for its height is very similar to the measuring process for the width of your window. You'll need to take three different measurements again. All three measurements will be taken from the top jamb down to the window sill.

The first measurement you should take is on the far left, measuring from the jamb to the sill. Then you'll repeat that process in the middle and on the far right.

For proper measuring, be sure to remember that the sill is the bottom horizontal point of the window where the sash rests when you close your window. It is important to remember that the sill is not the horizontal trim board that is a part of the wall.

While some people mistakenly call that board the window sill, it is actually the stool of the window and is not needed for your window measurements. You'll need to open your window in order to access the sill. Once you're done, write down the measurements that you obtained.

5. Measure Your Window's Depth

With most replacement windows, depth is not an important measurement to take. This is the case in most traditional homes, but if you're looking for a window replacement for a mobile home then you'll need to measure for depth.

The issue with the depth of the window is that if the depth isn't narrow enough then the window frame might not accept the replacement window. 

You can determine your window's depth by opening the window and measuring the amount of space the sill takes up from the front trim to the back trim. The depth of the window should be at least 3 1/4 inches for fitting a replacement window.

6. Round Down the Numbers

Once you've completed the task of measuring all of the windows you're wanting to replace, the next step is to take the shortest measurements on each window and round them down.

You'll want to round these measurements down by 1/8 of an inch. If a measurement is 35 and 15/16 inches then you'll want to round it down to 35 and 7/8 inches. This is only the case if your original measurement isn't already in eighth-of-an-inch measurements. 

After rounding down, you'll use these measurement numbers as the measurements for ordering your new replacement windows for your home. Getting the right measurements will help you get the right windows the first time around. 

It will save you time, money, and a fair bit of frustration compared to getting the correct windows the first time around.

7. Purchase Your Replacement Windows

When you're ready to get the replacement windows for your home, you have options. There are tons of online windows retailers that you can pick out your new windows from. There are also companies that focus on window replacement near me.

Brick and mortar locations for window replacements will usually carry some stock of windows in their location but even if you go through them you'll likely need to order windows that are customized to fit the measurements you need.

If worse comes to worst, you'll be best off having a service technician at your preferred window shop place an order on your behalf using the exact measurements that you took from your current windows at home.

While the window store might have windows on the shelf that could work, it is very unlikely that they'll be a perfect fit. This can lead to drafts, water damage, and other issues that will cost you more money in the future. The best approach is to order custom-fit windows and be patient while waiting for them to arrive.

A part of why custom orders are a great idea is that the window manufacturer will remove 1/4 of an inch from your measurements and build a new replacement window for you that is within 1/8 of an inch to give your new window the best fit possible.

Get Your Window Replacement Today

Knowing how to measure windows is vital if you're going to get replacement windows that are a perfect fit for your home's window frames. The best way to measure is by making sure the window is in square.

Then measure the width of the window, followed by the height of the window. If the window is in a mobile home, you'll also want to be sure to measure the depth of the window before purchasing replacements.

For more great and informative blog posts covering a variety of topics be sure to check out more of our blog!


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