How to Measure For Replacement Windows

Measuring for replacement windows ensures purchasing the correct size.

Replacing drafty, old windows is an expensive project. One way to save money on the project is to do some price shopping. The best way to shop for replacement windows is to know what size and how many windows you need. There are two methods of self measuring for replacement windows. Most manufacturers price windows based on the measurements of the existing window. However, if you have an older home, it might be necessary to measure the rough opening due to the settling of the home.

 Difficulty: Moderately Easy


       Things You'll Need:

  • Tape Measure
  • Pencil
  • Paper
  • Pry Bar  (note: use a small pry bar not a larger wrecking bar)

 Measuring The Window Opening 

1.   Place the end of the tape measure on the inside of the left surface jamb of the frame at the bottom of the window. The surface jamb is the channel where the window travels. Measure over the the inside right surface jamb.

2.    Write the measurement down and take the measurement again at the top of the window and the center of the window. The smallest of the three measurement is the width of the window.

3.   Position the end of the tape measure on the inside head surface and measure to the high point of the sill. The high point is the part of the sill where the window travels. Take this measurement on the right, center and left side of the window. The smallest measurement is the height of your window. 

 Measuring The Rough Opening 

1.  Pry the window trim away from the inside wall with a small pry bar. Start at one corner and lift the trim away from the wall. Move the pry bar up the trim, and continue prying it away from the wall. Repeat for all four sides of the window. This gives you a clear view of the rough window frame. 

2.   Measure the width of the window frame at the bottom , middle and top of the opening. Place the end of the tape measure on the inside of the left side stud and measure to the inside of the right stud. The window casing attaches to the house studs. Take the smallest of the three measurements as your width. 

3.   Place the end of the tape on the inside of the window frame header and measure down to the window sill frame board on the left side, right side and center of the rough opening. Take the smallest measurement as the height. .