measuring for replacement windows

Measuring for replacement windows takes knowledge, skill, and accuracy – and it’s more complicated than you would think. However, if you are in the market for a new double-hung window or sliding window, you need to obtain accurate measurements of the window opening. 

Grab your tape measure – it’s time to learn how to measure windows.

How to Measure for Replacement Windows

It’s important to note that your identical bedroom windows may not be the exact same size. So, here’s how to approach each window to record an accurate measurement.

Step 1: Inspect the frame for damage.

Replacement windows have to be attached to a window frame. Therefore, if the existing frame is damaged, the problem needs to be addressed before a new window can be installed

If the window frame shows no damage or rot, you can proceed to the next step. 

Step 2: Ensure the window frame is square.

All four corners of your window frame need to be “square.” This means that each corner must form a 90-degree angle. Here’s a method for determining if your window frame is square:

  • Hold the tape measure taut and measure diagonally from the inside of the upper left corner (where the horizontal and vertical trim boards meet) to the inside of the lower right corner.
  • Measure in the other diagonal direction. 
  • The window frame is suitable for a replacement window only if the two numbers are within ¼-inch of each other.

Don’t skip this step! Installing a replacement window in a lopsided frame can result in a window that won’t open.

Step 3: Prepare a place to record your measurements.

If the window frame looks and feels solid and is square, you are ready to measure for replacement windows. Again, it’s vital to be accurate during this process – in your measuring and recording. 

If measuring multiple windows, ensure the sets of measurements are clearly labeled. For example, your record sheet will show sizes for the “east bedroom window” and “west bedroom window.” Avoid using “right” and “left” to label windows.

Step 4: Measure the width of the windows.

Measure the width of your existing window at the bottom, middle, and top. 

Measure the distance from jamb to jamb. The jamb is the vertical board along the outer frame of the window. The sash slides along the jam when you open and close the window.  

Your window should be open when measuring the bottom and middle width. Close the window to measure the width at the highest point. 

Once all your measurements have been taken, circle the shortest measurement. 

window opening

Step 5: Measure the height of the windows.

Measure the height of your existing window at the far left, middle, and far right. 

Measure the distance between the top horizontal board above the window to the bottom sill. Please note that the sill is not the trim board that extends into the room. Instead, the sill is the board where the window sash rests when the window is closed

Your window will need to be open to get accurate measurements. Again, circle the shortest of the three measurements. 

Step 6: Measure window depth. 

In most houses, window depth isn’t an issue. However, windows in mobile or modular homes may not be deep enough to accept a replacement window.

Step 7: Round down to the nearest 1/8 of an inch. 

The shortest measurement in each set needs to be rounded down to the nearest 1/8 of an inch. For example, if one of your height measurements is 31-15/16 inches, round it down to 31-⅞ inches. 

For Accurate Replacement Window Measurements, Contact Woodbridge Home Solutions

We warned you that measuring for replacement windows takes a lot of knowledge. You may be the most accurate person with a tape measure, but still, record inaccurate measurements because you need clarification on the inside window trim and the window opening. Lucky for you, Woodbridge Home Solutions can help.

Schedule a free in-home estimate with Woodbridge if it’s time to replace your windows in Lubbock, Amarillo, or Dallas. You won’t have to worry about width measurements and window sizes. Instead, we’ll check and double-check the opening size, so you can be assured that your new windows will fit perfectly. 

Key Takeaways About How to Measure a Window Opening

  • Analyze the condition of your window frame. It must be free from damage and square before you take width and height measurements for your replacement window.
  • Take care to label all of your measurements using the location of the window in the home. 
  • Measure the width and height at three points on the window. Record the smallest number – to the nearest 1/8 of an inch.
  • You must be accurate when measuring for replacement windows. 
Categories: Information, Windows