Cabinet Door Calculator

Measure every opening individually

Measure width at the top, middle, and bottom, then measure height at the left, center, and right. Cabinet openings that look square can vary by 1/16 inch or more. For inset work, use the smallest relevant dimensions and check diagonals because the door must fit inside the opening with an even reveal. For overlay work, note any neighboring doors, finished ends, fillers, walls, and appliances that limit how far the door can extend.

Label each opening and keep its measurements with the finished door. Do not assume a run of cabinets has identical openings just because the boxes share a catalog size. Face-frame joints, installation shims, and finishing can create small but important differences.

Calculate an overlay door

An overlay door covers part of the face frame or frameless cabinet side. Add the chosen overlay at both edges of the opening. A 1/2-inch overlay adds one full inch to opening width and one full inch to opening height. Hinge cup location, edge thickness, adjacent door clearance, and cabinet construction determine which overlay is valid, so use the hinge maker's mounting table rather than choosing only by appearance.

For paired doors, the calculator first finds the total covered width, subtracts the desired center reveal, and then divides the remainder by two. Subtracting the reveal after division is a common mistake that makes the pair too narrow. Check the resulting outer overlays as well as the center gap.

Calculate an inset door

An inset door fits within the opening, so edge clearances are subtracted rather than overlays added. A 1/16-inch gap on each side removes 1/8 inch from width and height. Seasonal movement matters: a wide solid-wood frame can swell in humid conditions, while a narrow winter reveal can disappear in summer. Species, grain orientation, shop humidity, and finish all influence the practical clearance.

A perfectly calculated rectangular door cannot create an even reveal in a racked opening. Correct the cabinet when possible, or size the door to the smallest opening and plane or fit the edges deliberately. Inset doors often benefit from making a test panel or leaving a small amount for final fitting after the hinges are installed.

How the Shaker part dimensions work

The cut list assumes two full-height stiles and two rails fitted between them with cope-and-stick joinery. Rail length equals finished door width minus two stile widths plus two groove depths. The added groove depths represent the rail tongues entering the stiles. Different joinery changes that math: stub tenons, mortise-and-tenon joints, loose tenons, and simple butt joints each require their own allowances.

The center panel dimensions include the portion captured in the frame grooves. Panel width equals the visible opening plus engagement on both sides, then any intended expansion reduction must be applied. Verify your actual cutter profile with a test joint. Catalog descriptions such as “3/8-inch groove” may describe a nominal profile that does not match the measured shoulder-to-shoulder distance.

Allow the center panel to move

A plywood or MDF panel is relatively stable and can be sized with a small assembly clearance. A solid-wood panel moves across its grain. Do not glue a solid panel into all four grooves. Estimate seasonal movement for the species, panel width, grain direction, and humidity range, then leave room for expansion while maintaining enough groove engagement at the driest condition.

Finishing the panel before assembly can prevent an unfinished line from appearing when it shrinks. Space balls or other flexible retainers may reduce rattling without locking the panel. Follow the finish and adhesive manufacturer's instructions for compatibility.

Hinges, reveals, and neighboring doors

Door dimensions alone do not guarantee a successful installation. Confirm hinge boring distance, cup depth, plate height, opening angle, and required edge thickness. Adjacent doors need enough clearance to open without their edges colliding. A door beside a wall or deep appliance panel may need a filler or reduced overlay.

For a bank of paired doors, decide whether every center reveal and outside reveal should match visually. Small rounding differences are best handled in a coordinated layout, not corrected independently after every door is built. Record one reference dimension and verify the full run before milling parts.

Example and pre-cut checklist

Suppose an opening is 18 by 30 inches with a 1/2-inch overlay on every edge. The finished single door is 19 by 31 inches. With 2.25-inch stiles and a 3/8-inch groove, each rail is 19 − 4.5 + 0.75 = 15.25 inches before any tooling-specific adjustment. That arithmetic is useful only after confirming the hinge supports the selected overlay and the cutter produces the assumed groove engagement.

• Measure each opening in several places and compare diagonals.
• Confirm overlay or inset clearance from the actual hinge system.
• Measure finished rail, stile, and panel stock rather than nominal sizes.
• Test the cope-and-stick profile before cutting a full door set.
• Plan panel movement, finishing sequence, and final fitting.