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Wondering How to Measure Windows for Replacement? Here Are 5 Very Easy Steps to Follow

Removing old windows and replacing them with newer, more energy efficient ones helps to weatherproof a home and raise resale value. When the time comes for you to replace a home’s old windows, it is vital that you know the exact size of the window you want to replace.

If you are a homeowner, understanding how to measure for replacement windows helps you to provide accurate information to your contractor. If you are a contractor working on a project, the correct measurements help you to figure your costs for your quote, since size is a major factor in the pricing of new windows.

How to Measure For Full Frame Replacement Windows

Knowing how to measure for replacement windows is an intricate process that most homeowners and even many contractors struggle to fully understand. The tips below will show you how to measure for full frame replacement windows for the perfect fit.

1. Accurately Record Your Measurements

When buying a replacement window, it is essential that you get everything absolutely spot-on. If any measurement is off even by as little as an eighth of an inch, the window that you purchase could be completely unusable. Depending on the warranty offered by the manufacturer of the replacement window, you could find yourself having to start from scratch by buying new windows again.

No matter if you are replacing one or multiple windows, you should carefully record each measurement as soon as you take it. You may enter the details in a downloadable replacement window measurement worksheet or simply keep a record in a notebook.

2. Check Windows for Square

The first measurement you need to make is to determine if the existing window frame has 90-degree angles on all four corners. If you attempt to install a replacement window within a frame that is lopsided, the window might not open. Here’s how to measure casement windows for square corners.

Hold your tape measure taut, then measure the window diagonally from the lower right-hand corner of the window to the upper left-hand corner, and record your measurement. You should then measure the window in the opposite diagonal direction as well and record the measurement too. If the numbers are within a quarter inch of each other, then your frame is in square and the frame will fit a new replacement window.

3. Measure the Width of Your Windows

Next, you should measure how wide your window is in three places – the bottom, the top and at the middle. When you measure for width, you should position your measuring tape on the window jamb on either side of the frame. The window jamb is a vertical board that the window’s outer frame slides along when you close or open the window.

  • Bottom: Slide up the window and take a measurement from the lowest point of the jamb on one side to the jamb on the other.
  • Middle: Slide the window fully open and then take a measurement from one jamb to the other from as close to the middle as you can.
  • Top: Close the window, then measure its highest point from jamb to jamb to get the top measurement.

Once you capture all three, circle the shortest one.

4. Measure Window Height

Similar to the width measurement, you need to find out the height of the window. Once more, you should take three separate measurements, with each of them taken from the bottom sill to the horizontal board at the top of the window. Measure the length on the left, the right and one at the middle of the window.

When trying to find how to measure for replacement windows, you should know that the sill is not the trim which extends from the bottom of the window into the room. Instead, it is a horizontal board that supports the window sash when you close the window.

As with the width, take the measurements and highlight the shortest of the three.

5. Measure the Window Depth

When looking at the size of replacement windows on sale, the depth measurement is ignored since, in most cases, the depth of the window is not an issue. Depth only comes into play if your wall is too narrow to accept a standard replacement window, which may happen for mobile and modular homes.

To establish the depth in this case, you should measure the window sill space starting from the front trim to the back trim. Often, the space should be at least 3¼  inches to ensure your replacement window is a fit.

6. Round Down the Measurements

After measuring each window to be replaced, take the highlighted measurements, which are the smallest numbers in each set, and round down to the nearest one-eighth of an inch. The numbers you get are the measurements you should use to order replacement windows.

Replacement Windows from Top Manufacturers

The Pro Gallery is your one-stop shop for replacement windows in the Harrisburg area. We have a 7,000+ square foot showroom and a comprehensive selection of windows. If you are looking for how to measure for full frame replacement windows, we are happy to help you find the perfect replacement windows!

Visit our showroom and check out our window lines. Our in-house experts will show you how to measure for new construction windows.