How to Calculate the Rough Opening of a Door

The rough opening is the hole cut into a wall, during construction, where your new door will hang. Most doors are pre-hung, which means the door is already attached to a frame; you install the frame around the rough opening. You need a hole that is slightly larger than the door and frame. The extra space allows you to slide the door into place easily and adjust it within the hole to ensure the frame is square. Installing the frame square is essential for the door to open and close without sticking.

Step 1

Read the information provided by the door manufacturer. Look for specifications for the rough door opening if the information is provided. This gives you a general reference point to ensure the opening's measurements are suited to the door and frame you want to install.

Step 2

Measure the width of the entire door and frame that is attached. Take accurate measurements to ensure the rough opening isn't too large or too small. Add 1 inch to the width of the door to calculate the width of the rough opening. The extra width allows the door to fit easily into the opening.

Step 3

Measure the height of the entire door and attached frame. Add 1 inch to this measurement for extra space above and below the door for an easier fit.

Step 4

Mark the measurements for the rough opening on the wall. Hold the door and its frame up to the wall to get a visual to ensure the door frame will fit within the opening you measured.

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