Key takeaways
- Measure width and height in three places each
- Use the smallest number, and measure the frame, not the trim
- Have the order checked before it is made
Measure in three places
Old openings are rarely square, so measure the width at the top, middle and bottom, and the height on the left, center and right. Use the smallest of each set.
Measure the inside of the frame where the new window will sit, not the outside trim. Write the numbers down with the room name.
What the numbers mean
Replacement windows are usually made a fraction of an inch smaller than the opening so they fit and can be shimmed level. The exact allowance depends on the window and the installation method.
That is why ordering from your own measurements without a check is risky, and why we offer to verify.
Check the details
Note which way the window opens, whether there are grids and what the glass looks like. Check for rot at the sill with a screwdriver, since rotted frames change the plan from insert to full-frame.
Our Measure Guide walks you through the steps and shows the numbers on a drawing.
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Quick answers
Should I measure the old window or the opening?
Measure the opening the new window will sit in, from the inside of the frame. Your installer will confirm it.
What if my window is not square?
Use the smallest measurements and tell your installer, who can shim and fill the gaps.
Ready to talk it through? Get a free estimate or call 800-224-9245.