Enter your Door Width, Height, Thickness, Frame Type, and clearance values — Top, Side, Bottom, and Shim Space — and the Door Size Calculator figures out your Rough Opening Width, Rough Opening Height, Frame Width, and Frame Height so you know exactly what to frame.
Rough Opening Width
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Rough Opening Height
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Frame Width Required
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Frame Height Required
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A rough opening is the framed opening in a wall where a door will be installed. It must be larger than the actual door to accommodate the frame, shims, and proper clearances for installation and operation.
Standard clearances are typically ⅛" on top and sides, and ¼" on the bottom. These gaps allow for proper door operation, seasonal wood movement, and carpet or flooring thickness.
Interior doors are typically 1⅜" thick, while exterior doors are usually 1¾" thick for better insulation and security. Heavy-duty applications may use 2" thick doors.
Allow at least ½" of shim space around the door frame for proper leveling and square adjustment. This space is crucial for achieving a professional installation.
Yes, different frame materials have varying thicknesses and installation requirements. Steel and aluminum frames may require different clearances compared to wood frames.
Custom doors can be made to fit non-standard openings. However, it's often more cost-effective to modify the opening to fit standard door sizes when possible.
Yes, if installing a raised threshold or adjustable sill, add its height to your rough opening calculations. Standard thresholds are typically ¾" to 1¼" high.
Measure the width at three points (top, middle, bottom) and use the smallest measurement. For height, measure both sides and use the shortest. Always measure to the nearest 1/16".