How to Measure Windows for Replacement – a Complete Guide for You

Last updated on December 14, 2023

Upgrading your windows can help enhance your home’s curb appeal and breathe new life into the interiors. Replacing old and damaged windows also makes your home more energy-efficient. If you are planning to replace your existing windows, start by measuring them correctly. Having an accurate size estimate can help you shop for new windows and ensure you have the right fit. Not sure where to get started? Read on to get an idea:

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5 Simple Steps to Measure Your Old Windows for Replacement

5 Simple Steps to Measure Your Old Windows for Replacement

Measuring your windows for replacement is a simple DIY task. Following these six steps will help you measure your old windows accurately and prepare for replacements. 

Know the Parts of a Window

Styles may vary, but the basic anatomy of windows remains the same in most cases. Knowing the parts of a window frame will help you measure accurately and purchase replacements that fit your window openings. 

  • Sash: A sash is the fixed or moveable part of the window frame that firmly holds the glass pane.  
  • Jambs: The vertical components located on either side of a window frame touching the sides of the sash are called jambs.  
  • Head of the window: The horizontal element at the top of the window frame is known as the header or head. It runs across the top edges of the jambs, while the top ends of the upper window sash rest against it. 
  • Sill: It is the horizontal element at the bottom of the window frame and runs across the bottom edges of the jambs. The bottom ends of the lower window sash rest against the sill.   

Determine if the Old Window Frame is a Square

Window sizes may be different, but replacements mostly come in squares with 90-degree corners. The level helps measure the horizontal straightness of the window frame, whereas the plum determines the frame’s vertical straightness. Below are the steps to check if the existing window frame has a square alignment: 

  • Hold the measuring tape on the top right corner of the frame where the horizontal and vertical jambs meet and take the measurement. 
  • Now stretch the tape and measure diagonally to the bottom left side of the window frame where the jambs meet. 
  • Repeat this same process to measure the window frame from the top left side diagonally to the bottom right corner. 
  • Most standard replacement windows will fit in the opening if the above two measurements are within ¼-inch of each other.  

Measure Window Height and Width 

Replacement windows come with precise width-by-height measurements. Therefore, you need to measure your existing window’s height and width accurately for perfect installation. Measure the right side, middle, and left side of the window to find the height. The height measurement should extend from the window’s header to the bottom where the sash rests when you close the window. Take three measurements and the shortest one is the height of your window opening. 

To get the width, you need to measure the inside of each jamb. Ensure you close the window and calculate the distance between the top two window jambs. Now, open the window and take the measurements between the jambs nearest to the center of the window. Next, take the measurements between the right and left bottom jambs. The smallest of these three measurements indicates the width of your window opening. 

Measure the Depth of the Window Opening 

Some replacement windows may be too deep to fit perfectly into the existing window opening. Therefore, measuring the correct depth is crucial. For this, you need to run the measuring tape from the outside to the inside of the window frame and compute from trim to trim. Repeat this process in different parts around the frame and the smallest measurement is your final depth. 

Measure Your Window Screens

There are two ways you can measure window screens for replacements. If you want to replace the existing one, calculate its height and width to get the perfect replacement window screen.  

The Takeaway

The above-mentioned steps will help you understand how to measure windows for replacement.

Finding the right replacement windows requires accurate measurements to determine the perfect fit. Always double-check the measurements to ensure they are correct before you order new windows or try to install one. It is always a good idea to work with a professional like Advance Roofing LLC who can precisely take your window measurements and install the best replacement.

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