Measurement Guide

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Jamb (Frame) width. Measure from the backside
of the interior trim to the backside of the exterior
trim (Figure A). Specify this jamb width when you
order your new prehung door. This guarantees
that the interior trim will fit flush to the wall
without adding “jamb extensions.”
Rough opening. You’ll have to remove the
interior trim to get accurate measurements of
the rough opening. Measure the opening width
between framing members and from the bottom
of the sill to the top of the opening. Compare
these measurements to the rough opening
requirements of your new door to make sure it
will fit.
How to accurately measure rough opening
 Measure the widths between the studs of the entryway 3 times; from the highest points of the
opening, the center points, and the lowest points. Record the smallest width of the 3
measurements.
 Measure the height (from the bottom of the sill to the top of the opening) on both sides and
record the smallest measurement of the 2.
Rough opening recommendations
Getting the rough opening size right the first time will save you from frustration when installing your
doors. Framing and calculating rough opening sizes is quite simple.
Tip:
Not all rough openings are completely plumb and square. Leaving extra space allows you to perfectly
plumb, level and square your door installation.
Single Door
Frame (Unit) Dimension:
Width: Add 1-1/2 in. to the width of the actual door