How to Measure A Window for Replacement: 3 Easy Steps

Measuring for a replacement window is an essential step if you’re ordering or installing windows yourself. And to do it, all you need is a tape measure, a pencil, and a piece of paper.

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You can follow the three easy steps below to measure replacement windows accurately. Remember to double-check your measurements to ensure the windows you order will fit. 

How to Measure for a Replacement Window

You can measure for replacement windows in three steps. You’ll need a tape measure to determine your window’s width, height, and depth.

And remember, when ordering windows, measurements are width x height.

Step 1: Measure the Width of Your Window in Three Places

You’ll start by measuring the width of your window between the side jambs. If possible, move the window sash out of the way so it doesn’t interfere with your measurements.

Now measure the width of your window in three places: the top, the bottom, and the middle.

Write down all three measurements. The smallest of the three is your window’s width.

Step 2: Measure Your Window’s Height

You’ll repeat the previous step, only measuring the height of your window in three places: the far left, the center, and the far right.

Your measurement should run from the head jamb down to the windowsill. Again, move the sash out of the way when measuring.

Write down your measurements as you go. The smallest is the height of your window.

Important note: if your window isn’t rectangular or has an arch on the top, measuring height is a little different. Start by finding the center of the window. Then, measure from the top center to the face of the frame and add ½ inch – that’s the height for your window.

Step 3: Measure the Jamb Depth

Now, find the deepest part of your window and take its measurement. Take this measurement in several areas – the smallest number is your window depth.

(While you don’t need a window depth measurement to order replacement windows, ensure your window depth is at least 3 ¼ inches. Otherwise, it’s too narrow for most windows to fit.)

How Do You Check if your Window Frame is Square?

For a replacement window to fit securely in your existing window frame, it must be square. If not, you’ll need to correct the frame.

Here’s how to check:

  • From the inside of your home, measure your window frame diagonally from the top right corner to the bottom left corner – write down the measurement
  • From inside your home, measure your window frame diagonally from the top left to the bottom right corner – write down the measurement.

If the measurements are within ¼ of an inch of each other, your frame is suitable for replacement windows.

Frequently Asked Questions (FAQ)FAQ

Do companies measure windows for a new window quote?

Schedule an in-home consultation with a window installation company if you don’t feel confident measuring your windows. They’ll come to your house, measure your windows, discuss options, and give you a price quote.

Will Home Depot measure for replacement windows?

If you schedule an in-home consultation with Home Depot, they will measure your windows before giving you a quote and remeasure before they place the window order.

Do you measure windows from the inside or outside?

If you’re measuring for replacement windows, take measurements from inside your home.

Final Thoughts

Getting accurate measurements for your replacement windows is vital for good-fitting windows. Measure the width and height in three parts of the window – then go with your smallest measurements. Take your measurements a couple of times to ensure they’re correct.

Many issues can arise from mismeasuring or installing windows. If you don’t feel qualified, contact a local window professional or contractor, or use a window installation service from the window brand.