How to Measure for Replacement Windows

To accurately measure for new full-frame replacement windows, you need to measure the rough opening. You can remove the entire existing window and measure the frame, but new windows can take weeks, even months, to arrive after ordering. A better way to accurately measure your window's rough opening is to drill a couple of small, unobtrusive holes into the interior wood frame. These holes will be plugged and made nearly invisible when the new windows are installed.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Tape measure Drill (if necessary) 6 to 12 inches of stiff wire (part of an old wire coat hanger works well)

1. Drill a small hole into the left side of the window jamb near the top of the window. If there is an existing small hole in the jamb that houses the window pulley apparatus, you won't need to drill; simply use that. (The pulley apparatus is the rope that holds the weight which keeps your windows open. If your window won't stay open without being propped up, the weight has most likely separated from the rope.)

2. Insert the length of stiff wire into the hole you drilled or the existing pulley rope opening, and feed it in until it stops. Grasp the wire with your thumb and finger at the edge of the frame and remove the wire without moving your finger and thumb. Measure the length of the wire from the point where your fingers are to the end of the part of the wire that you inserted into the window frame. Write this measurement down.

3. Repeat Steps 1 and 2 for the right side of the window. Drill the hole for measuring at the same spot in the right hand jamb as you did in the left hand jamb.

4. Measure the width of the window from jamb to jamb at the point where you drilled the holes.

5. Add these three measurements to get the correct width of the rough opening of your window.

6. To measure the height of your window, first drill a small hole at the bottom. Place the hole at the center of the window, right next to the sill, directly under where the window's sash rests when the window is closed. Insert the wire as you did in Step 2, measure the window and record this measurement.

7. Drill a small hole in the top jamb of the window, directly above where you drilled the hole in the bottom. Insert wire as before, measure and record.

8. Measure the window opening from sill to top jamb at the point where you drilled the holes.

9. Add all three measurements together to arrive at the correct height of the rough opening of your window.

Tips & Warnings

• Some older homes do not have a header (supporting wood frame) above the window. If your wire isn't stopped when you insert it when measuring at the top of your window, you'll need a contractor to remove the existing window, frame the top of the opening and then measure for the replacement window.