Tips on how to correctly measure a window

“Replacing a window doesn’t have to be a major headache. Following basic guidelines and recording exact measurements will help make the process seamless and the end result painless.”

Gary Mathes
Manager, Residential Architectural Services
Pella Corporation

Proper measurement of windows is essential in successfully installing new or replacement windows in a home. Following these Pella® guidelines will help ensure precision and therefore, best performance of new windows. These recommendations are based on the installation of a typical replacement wood or vinyl double-hung window into an existing wood double-hung window frame.

How to measure a window

  • Width
    • Using a tape measure, measure the width from the inside of the jamb on one side of the window to the inside jamb on the other side of the window; the jamb is one of the vertical fixed-frame pieces on each side of the window frame
    • Repeat this step at the bottom, middle and top of the existing installed window
    • Record the shortest measurement
  • Height
    • Measure the height from the head of the window (top fixed-frame piece) to the windowsill (bottom fixed-frame piece)
    • As with the width, take three measurements: down the left side, right side and the middle
    • Record the shortest measurement — this ensures that the new window will fit

Tips for measuring windows

  • Measuring only to the sash stops and the interior trim of the windowsill will result in the new window being too small (the sash stops are the small square wood pieces at the top and sides of the window that keep the venting sash securely in place)
  • Take all measurements from inside the home
  • Accuracy is key — this will ensure the windows install properly, and will help to maximize energy savings
  • When planning a window replacement project, it's important to approach the steps in your project in the right sequence. Measure your windows first, then choose, purchase and receive your replacement windows. Only then should you remove your old windows to make ready for your new windows.
  • A basic replacement window project should take about an hour to complete; the time may vary based on your project’s unique needs
  • Once the new window is in place, be sure the window is square — the window frame should sit perfectly square with the sides straight
  • Remember owning a home is one of the best investments a person can make; keeping it properly maintained will contribute to a maximum return on investment

Further questions?
Contact your local Pella® Window & Door Showroom or call 888-84-PELLA or visit www.pella.com/news.