Dado Width and Depth Calculator
Calculate dado (housing) joint dimensions for shelves, drawer sides, and cabinet construction.
Find optimal dado width, depth, and router bit setup for a perfect fit.
What Is a Dado? A dado (also called a housing joint in the UK) is a rectangular channel cut across the grain of a board. It is used to accept a shelf, drawer bottom, divider, or panel — creating a strong, flush joint. A groove is the same cut but with the grain (along the length of the board). Dado joints are fundamental in cabinet making, bookcase construction, and drawer building.
Standard Dado Rules Width: equal to the thickness of the mating piece (with a tiny allowance for fit). Fit allowances: Snug fit: exact nominal width (plywood may be undersized — verify with calipers). Sliding fit: add 0.5 mm (0.020") to nominal width. Loose fit (for removable shelves): add 1 mm (0.039"). Depth: traditionally 1/3 of the workpiece thickness (good structural rule). Maximum: never exceed 1/2 of the board thickness (weakens the board significantly). Minimum: 6 mm (1/4") for most loads.
Plywood Thickness Reality Nominal 3/4" (19 mm) plywood is almost never 19 mm — it measures 18.0–18.5 mm. Nominal 1/2" (12.7 mm) plywood typically measures 11.9–12.4 mm. Always measure your actual plywood with calipers before setting dado width. Baltic birch plywood is more consistent; American softwood plywood varies most.
Router vs. Table Saw Dado Table saw dado stack: most common for production. Stack set of chippers adjusts width precisely. Router with straight bit: accurate for narrow dados; requires edge guide or dado jig. Router with template guide: for repeated cuts in batch production. Plunge router: for stopped dados (doesn’t run to edge of board).
Stopped Dado A stopped dado doesn’t run all the way to the front edge — gives a cleaner look. The mating piece has a notch cut to clear the stopped end. Stopped width: calculate as normal; the stop point is typically 1"–2" from the front face.
Structural Notes A dado carries the shelf’s load in shear. Proper depth is critical. Too shallow (< 6 mm): insufficient shear area, shelf may pull out under load. Too deep (> 50% of board): board may crack or break along the dado plane. Glue in the dado adds significant strength.