Start with the real cabinet opening
Measure the finished opening rather than relying on the drawing or nominal cabinet size. Check the width at the top and bottom and the height at both sides. If the measurements differ, the cabinet is not perfectly square and the smallest useful dimension may be the safer starting point for an inset door.
How to calculate inset and overlay cabinet door sizes
An inset door sits inside the opening, so the chosen gap is removed from every outside edge. An overlay door sits in front of the cabinet and extends beyond the opening, so the chosen overlay is added at every outside edge.
For a pair, the centre gap is removed once from the total available width before it is divided between the two doors. The calculator assumes both doors are the same width.
Door-sizing formulas
A single inset door is opening width - 2 × edge gap byopening height - 2 × edge gap. A single overlay door adds twice the overlay instead. For paired doors, subtract the centre gap from that overall door width and divide by two.
Worked example: paired overlay doors
For a 600 × 720 mm opening with 12 mm overlay on every outside edge and a 2 mm centre gap, the doors cover 624 × 744 mm overall. After removing the centre gap and dividing the remaining width, each door finishes at 311 × 744 mm.
Check the hinges before cutting
This calculator does not choose a hinge or calculate cup-hole positions. Concealed hinges have specific overlay ranges, mounting-plate combinations, boring distances and minimum gaps. Confirm the finished size against the hinge manufacturer's instructions and your actual cabinet construction before cutting the doors.
Edge profiles, paired-door lips, face frames and unusually thick doors may need more operating clearance. Make a sample corner or test door if the fit is unfamiliar, and leave enough material for your planned trimming and finishing process.
Common questions
Is overlay measured on each side?
Yes. The overlay input is the amount the door extends beyond the opening at each outside edge. The total door width therefore gains twice that amount for one door.
What gap should I use for inset doors?
There is no universal answer. It depends on how square the cabinet and door are, hinge movement, material stability and the finish. Choose a gap your build can reliably hold, then verify it with the hinges and a test fit.
Does the result include trimming allowance?
No. It is the intended finished door size. Add your own machining or trimming allowance when preparing rough parts.
How do I size double cabinet doors?
Choose a pair of doors and enter the gap wanted where they meet. The calculator removes that centre gap once from the total door coverage, then divides the remaining width into two equal finished doors.
Can I use this for Shaker cabinet doors?
Yes, for the finished outside size of each Shaker door. It does not calculate individual rail, stile or panel parts because those depend on the widths and joint depths used in your particular construction method.