How to Measure for Doors Including Door Jambs

When creating a new opening for a door, the measurement that takes into account the total dimensions of the door unit, including the jambs, is a measurement of the "rough opening." The door jamb is the vertical section of a door frame, which supports the frame to the wall and also supports the door itself. There is a jamb above the door, called a head jamb, and one on each side. The hinge jamb is located on the same side as the door hinges, and the latch jamb is on the same side as the door knob.

Tape measure

Instructions

- 1
  Measure the width of the door using a tape measure. Place one end of the tape measure on one edge of the door near the top and measure across to the opposite side, extending the tape measure to reach the opposite edge. Measure the door at a point across the middle and across the bottom as well. Record the shortest of these three measurements of the door width.
- 2
  Place the end of the tape measure on the top edge of one end of the door. Measure the height of the door, extending the tape measure to the bottom edge on the side of the door. Measure the height of the door on the opposite edge, measuring from top to bottom. Record the smaller of these two measurements.
- 3
  Add 2 inches to the smallest of the 3 measurements for the door width. This additional space will allow for the width of the side door jambs, plus give approximately 1/2 inch more room. Add 2 1/2 inches to the shorter of the height measurements to allow for space for the head jamb.

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