Article
How to Calculate Cabinet Parts
Cutlistor Team5 min read
Introduction
Calculating cabinet parts means converting a finished box width, height, and depth into every panel your saw or CNC must cut. Professional shops standardize those formulas so quoting, sheet POs, and production all use the same numbers.
This article focuses on case parts: gables, decks, shelves, backs, stretchers, and toe structure. Door, drawer, filler, and face-frame sizing have their own guides. Wrong case math is the most common reason a nest looks fine and the box still will not assemble.
Inputs You Must Freeze First
Write these values at the top of every takeoff. Changing thickness or joinery after nesting wastes a full sheet re-plan.
- Finished cabinet width (outside of box, or face-frame outside if that is how you quote)
- Box height and depth
- Panel thickness (18 mm / 3/4 in common for cases)
- Back thickness and joinery (inset, rabbet, or full overlay)
- Frameless vs face frame
- Butt joint vs dado / CNC groove depth
- Toe kick height and whether the toe is separate or integral
Frameless Case Formulas (Butt Joint)
| Part | Formula | Example (W=900, H=720, D=560, T=18) |
|---|---|---|
| Gable (each) | Depth × Height | 560 × 720 mm (qty 2) |
| Bottom | (W - 2T) × Depth | 864 × 560 mm |
| Fixed shelf | (W - 2T) × (Depth - setback) | 864 × 540 mm if 20 mm setback |
| Top stretcher | (W - 2T) × stretcher width | 864 × 100 mm (qty as needed) |
| Full top (if used) | (W - 2T) × Depth | 864 × 560 mm |
If you dado the bottom into the gables, bottom width becomes W - 2T + 2×dado_depth (or your CNC groove convention). Document the rule once and never mix butt and dado math on the same job without labeling it.
Back Panel Sizing
| Method | Width formula | Height formula |
|---|---|---|
| Inset flush to inside | W - 2T | H - 2T (if full top and bottom) |
| Rabbeted gables | W - 2×(T - rabbet) approx. | Match rabbet height |
| Full overlay back | W × H (or shop standard) | Often oversized then trimmed |
| Face-frame box | Opening inside frames ± rabbet | Confirm with frame reveal |
Face-Frame Case Adjustments
With face frames, the plywood or melamine box is often slightly smaller than the finished face-frame width. Some shops size the box to the inside of the frame; others build the box to finished width and apply the frame proud. Pick one standard.
Typical pattern: box width equals finished width, face frame applied to the front edge, or box width equals finished width minus frame overhang rules. Stile and rail lengths are linear stock, not sheet parts.
Toe Kick and Base Platform
Toe kicks may be a separate platform under the box, a recessed front rail, or a applied skin. If the box height excludes the toe, do not subtract toe height again from the gable. If the gable includes the toe notch, note the notch on the cut list so nesting does not treat it as a simple rectangle without CNC work.
Imperial Worked Example: 36 in Base
| Part | Qty | Cut size |
|---|---|---|
| Gable | 2 | 24 × 34-1/2 in |
| Bottom | 1 | 34-1/2 × 24 in (36 - 3/4 - 3/4) |
| Top stretcher | 2 | 34-1/2 × 4 in |
| Shelf | 1 | 34-1/2 × 23 in (1 in setback) |
| Back (approx. inset) | 1 | 34-1/2 × 33 in (verify joinery) |
Scaling Quantities for Production
For a run of eight identical 900 mm bases, multiply every unique part quantity by eight, then nest once by material. Do not nest eight separate single-cabinet layouts if they share the same melamine SKU. Label parts with cabinet numbers when boxes differ only by width.
From Formulas to Nest and Sheet PO
After the part matrix is complete, import or enter rows into a sheet optimizer. Set kerf to the panel saw blade or CNC bit. Lock grain on exposed ends. Read sheet count for the PO, then export a labeled PDF for the floor.
Most free optimizers meter the optimizing. Cutlistor does not — you can tweak parts and re-run the layout as often as a job needs. The daily ceiling of 3 applies to PDF exports and new projects only. Expect a 20-row cut list limit, a 5-row ceiling on each CSV or XLSX import, and no saved projects.
Pro at $12/mo adds saved projects and DXF export (paid) for CNC. Cutlistor remains a nesting and cut-list tool, not a full design suite.
FAQ
Should I calculate in millimeters or inches?
Match the units your machines and suppliers use. Mixed units on one cut list cause the expensive errors. Convert once at design intake, then stay consistent through nesting.
Do I use nominal or actual thickness?
Use the thickness you machine for. Many 3/4 in plywood sheets are slightly under; European 18 mm is usually reliable. Calibrate critical dados to measured stock.
Are doors included in case part formulas?
No. Door and drawer front sizes follow overlay rules. Keep them on separate rows so a style change does not corrupt case math.
Conclusion
Cabinet part calculation is standardized arithmetic: width, height, depth, thickness, and joinery rules produce every gable, deck, shelf, and back. Lock those rules, work a single box example, then scale quantities and nest by material.
Put the finished list into Cutlistor, set kerf, and buy the sheet count the nest proves, not a square-footage guess.