How to Measure for your New Replacement Window

How to Measure for your New Replacement Window


After you’ve chosen which window you want to purchase, you’ll need to measure for your new window.  Before you can do this, you’ll need to understand the parts of a window.  Here is some helpful information about how to measure windows.  Below is a diagram from Pella, one of the nations leading replacement window suppliers.


measure windows, replacement windows

1.Frame. The combination of the head, jambs and sill that forms a precise opening in which a window sash fits.


2.Glass. A framed sheet of glass within a window frame.


3.Grilles. Any bar that divides window glass into smaller panes. Also called a muntin, grid or windowpane divider.


4.Head. The main horizontal part forming the top of the window frame.


5.Jamb. The main vertical parts forming the sides of a window frame.


6.Sash. A single assembly of stiles and rails made into a frame for holding glass.


7.Sill. The main horizontal part forming the bottom of the frame of a window.


To measure for your new replacement window, focus on the jamb (identified as #5 in the image above), the sill (identified as #7) and the head (identified as #4).


Precision is key when it comes to measuring windows.  We recommend measuring for your new replacement window in 3 different places when calculating the vertical and horizontal measurements.



To determine the width,  measure from jamb to jamb.  Start by taking measurements at the top of the window.  Then, measure the middle of the window and lastly, the bottom of the window.



For the height, measure from the sill to the header.  Again, we suggest taking 3 measurements: one in the center, one on the right side and one on the left side.


Remember, it is not uncommon to get slightly different measurements.  When gathering a quote for your new replacement window, use the smallest measurements that you took for the width and height.


The measurements that you take are for pricing purposes only.  If you purchase windows, a professional installer make a site visit to confirm the accuracy of the measurements.