How to Measure a Door Opening for a New Commercial Door

Why Accurate Measurements Matter

Ordering a commercial door with incorrect measurements leads to costly returns, project delays, and installation headaches. Taking the time to measure correctly before ordering is the single most important step in the door procurement process.

Key Terms to Know

• Rough Opening: The framed opening in the wall before the frame is installed.
• Frame Opening (Masonry Opening): The opening size of the door frame itself.
• Door Size: The actual door leaf dimensions (width × height).
• Nominal Size: The labeled size (e.g., 3'0" × 7'0") which may differ slightly from actual dimensions.

Step-by-Step: How to Measure

Step 1: Measure the Width

Measure the width of the rough opening at three points: top, middle, and bottom. Use the smallest measurement. For a standard commercial door, subtract 2" from the rough opening width to get the door width (accounting for the frame).

Step 2: Measure the Height

Measure the height of the rough opening from the floor to the top of the opening at three points: left, center, and right. Use the smallest measurement. Subtract 2" to account for the frame.

Step 3: Measure the Wall Thickness

Measure the depth of the wall at the opening. This determines the frame profile (throat size) you'll need. Standard commercial frames are available in 4-9/16", 5-1/4", and custom depths.

Step 4: Determine the Door Swing

Stand in the opening facing the direction the door will swing. If the hinges are on the left, it's a left-hand door. If on the right, it's right-hand. This is critical for ordering the correct hinge prep and hardware.

Standard Commercial Door Sizes

• Single doors: 2'8" × 7'0", 3'0" × 7'0", 3'6" × 7'0"
• Double doors: 5'0" × 7'0", 6'0" × 7'0"
• Tall doors: 3'0" × 8'0", 3'0" × 9'0"

When to Call a Professional

If you're replacing a door in an existing masonry or concrete opening, or if the opening is out of square by more than 1/4", consult a professional installer before ordering.