A custom door needs more than a width and height. The opening, jamb, wall thickness, and swing direction all affect how the door fits and operates. Before ordering, gather measurements at several points and note any details that could change installation. A careful record helps you communicate clearly with the door maker and spot problems early. If the opening is irregular or the order involves a complex installation, have a professional verify the measurements before production begins.
Measure the Opening
For a replacement door, first determine whether you are ordering a door slab alone or a prehung unit with its frame. If you are replacing only the slab, measure the existing door’s width, height, and thickness. Do not assume a nominal size is the exact size; record the actual dimensions and note whether the door has been trimmed or altered.
For a new opening or prehung unit, measure the rough opening from stud to stud and from the floor or subfloor to the top of the opening. Take width measurements near the top, middle, and bottom, then height measurements on both sides. Record the smallest width and height, but keep every reading so the installer can assess whether the opening is out of square.
Check the Jamb and Wall
The jamb is the frame surrounding the door. For a replacement slab, note the existing jamb condition, hinge locations, hinge sizes, and the distance from the top of the door to each hinge. Measure the door thickness and check the lockset bore and backset if you plan to reuse the hardware. Photos of the hinges, strike plate, and edge can help clarify what must match.
For a prehung door, measure the wall thickness from the finished surface on one side to the finished surface on the other. Include drywall, paneling, tile, or other coverings. Record whether the jamb needs an extension, and note trim or flooring that could affect clearance. If the floor covering will change, tell the door maker or installer before final sizing.
Identify the Swing Direction
Stand on the side of the door where you would normally enter the room, with the door closed. Note which side has the hinges and whether the door opens toward you or away from you. In many ordering systems, handing is described as left-hand or right-hand, but conventions can vary, so confirm the supplier’s diagram before selecting an option.
Also consider how the door will move through the room. Check for nearby walls, cabinets, appliances, stairs, and other doors. Make sure the planned swing will not block a walkway or collide with furniture. For a double door, specify which leaf should open first and whether one or both leaves need to operate.
Know When to Get Verification
Ask a professional to verify measurements when the opening is noticeably out of square, the floor is uneven, or the jamb is damaged. Verification is also wise for exterior doors, oversized or unusually shaped openings, concealed hardware, and projects where the door must meet specific weather-sealing or accessibility requirements. A small measurement error can affect fit, security, and how smoothly the door operates.
Before placing the order, share your measurement notes, photos, door type, intended swing, hardware plans, and any upcoming changes to flooring or trim. Confirm whether the supplier needs rough-opening dimensions or finished door dimensions. Memphis Doorworks can help discuss custom door details; confirm the measurement and installation process directly before production.
Measure the opening in several places, document the jamb and wall thickness, and confirm the swing using the supplier’s terminology. Keep your notes and photos together, and do not guess when the opening or installation is complicated. If anything is uncertain, arrange a professional measurement before ordering so you can move forward with greater confidence.