How to use cabinet door finished sizing
What this calculation does
Door sizing converts an opening into equal overlay or inset door outside dimensions with explicit outside and center gaps.
Measure the opening, select overlay or inset, count equal doors, and enter only the clearance fields for that fit.
Enter the measurements
- Door fit: Choose overlay or inset; only its matching edge input is used.
- Opening width: Measure the clear opening width.
- Opening height: Measure the clear opening height.
- Equal doors across the opening: Count equal doors across the opening.
- Gap between doors: Enter the gap between adjacent doors.
- Overlay per outside edge: For overlay mode, use overlay at each outside edge.
- Inset gap per outside edge: For inset mode, enter the outside inset gap.
Formula and variables
Overlay overall width = opening width + 2 × overlay. Inset overall width = opening width − 2 × edge gap. Each door width = (overall width − (door count − 1) × centre gap) ÷ door count. Height adds the two overlays or subtracts the two inset gaps.
Overlay adds twice the overlay to overall width and height; inset subtracts twice the edge gap. Center gaps are deducted once between neighboring doors.
Read the result
Two overlay doors are each 15.4375×29 in for the stated 30×28 in opening and gaps.
Worked example
Inputs: 30 × 28 in opening, two equal doors, 0.5 in overlay per outer edge, 0.125 in centre gap
- Overall width = 30+2×0.5 = 31 in; each width = (31−0.125)÷2 = 15.4375 in.
- Height = 28+2×0.5 = 29 in.
Expected result: each door 15.4375 × 29 in
Frequently asked questions
Are the sample overlay values standard hinge clearances?
No. Confirm finished dimensions and overlay against the cabinet and selected hinge.
Does the paired page use the door size for its frame parts?
The second form is separate; enter its finished door dimensions and its own joinery values.
Conditions, presets and technical notes
Finished outside sizes for equal doors. Choose gaps and overlay from the actual construction and current hinge instructions. These are illustrative defaults, not standard hinge clearances. Add rough-machining allowance separately. A single door has no centre gap deduction.
