Dado Width Calculator

What Is a Dado Joint?

A dado joint is a rectangular channel cut across the grainof a board to accept a mating panel — the standard joint used in cabinet shelving, bookcases, and drawer assembly. The dado width must match the actual thickness of the panel, not its nominal size, since plywood is almost always slightly undersized.

The Dado Width Calculatordetermines the correct blade or router bit width for a snug-fitting dado, groove, or rabbet. Enter your panel’s actual thickness and the tool returns the precise cut width, depth setting, and recommended blade configuration for both table saw dado stacks and router setups.

Dado Width Formula

For a snug-fit dado that accepts a panel without play, the dado width equals the actual measured thickness of the mating material:

For a stack dado blade set where multiple passes are taken:

For dado depth, the standard woodworking rule is:

Actual Plywood Thickness Chart

Because plywood and MDF are nominally sized but actually undersized, your dado must match the real thickness. Use this reference chart when setting your dado blade or router bit:

How to Cut a Dado Joint

Using a Dado Blade Set (Table Saw)

1. Measure the actual thickness of your mating panel with a caliper.
2. Assemble the dado blade stack to match that width (use shims for fine-tuning).
3. Set blade height to 1/3–1/2 of workpiece thickness.
4. Use a test cut in scrap wood to verify fit before cutting the final workpiece.
5. Run the workpiece through with the mating face against the rip fence.

Using a Router

1. Select a straight router bit or spiral upcut bit matching your panel thickness.
2. Set the cutting depth to 1/3–1/2 of workpiece thickness.
3. Clamp a fence or use a guide bushing to control bit travel.
4. Route in a single pass for clean cuts; use climb cut to prevent tearout.

Frequently Asked Questions