Dado Blade Width Calculator
Find the blade width needed per pass to cut a dado or groove to an exact target width. Use it when your dado stack cannot be set to the exact groove width in a single pass.
About this calculator
A dado is a flat-bottomed groove cut across or along a board, commonly used for shelving, drawer bottoms, and cabinet backs. A dado blade stack is adjustable but has discrete width increments; sometimes your target groove width falls between available settings. The formula here is: Blade Width per Pass = Desired Groove Width / Number of Passes. If you need a 3/4″ groove but your dado stack maxes out at 13/16″, you can instead make two passes with a narrower blade setting, shifting the fence between passes to widen the groove incrementally. Understanding this relationship lets you achieve precise groove widths with any table saw setup, even without a full dado stack, by making multiple passes with a standard kerf blade.
How to use
Suppose you need a dado that is exactly 3/4 inch (0.75 inches) wide and you plan to make 3 passes with your table saw. Apply the formula: Blade Width per Pass = 0.75 / 3 = 0.25 inches per pass. Set your blade to 0.25 inches wide (or position your fence so each successive pass removes 0.25 inches). Make the first pass, shift the fence by 0.25 inches, make the second pass, shift again, and make the third pass. Test the fit with a piece of scrap at the same thickness as your shelf material before committing to the final workpiece.
Frequently asked questions
How do I choose the right number of passes when cutting a dado with a table saw?
The number of passes depends on your blade kerf width and the desired groove width. If your blade has a 1/8-inch kerf and you want a 3/4-inch dado, dividing 0.75 by 0.125 gives 6 passes — which is manageable but slow. Many woodworkers prefer 2–3 passes for efficiency. With a dado stack, you can usually get close to your target width in one or two passes by selecting chippers of the appropriate thickness and adding shims for fine-tuning. Use test cuts in scrap wood to dial in the exact width before cutting your workpiece.
What is the difference between a dado cut and a rabbet cut in woodworking?
A dado is a groove cut across the grain of a board (perpendicular to the length), while a groove runs with the grain (parallel to the length) — though both are flat-bottomed channels. A rabbet is a step cut along the edge or end of a board, removing only one shoulder. All three joints are used in cabinet and furniture construction: dadoes hold shelves, grooves capture panel bottoms and backs, and rabbets join case sides. The dado blade width calculation applies equally to all three cut types since the underlying geometry is the same.
Why is an exact dado width important for woodworking joinery?
A dado that is even 1/32 inch too wide will produce a sloppy, weak joint that requires excessive glue to fill gaps; one that is too narrow will prevent assembly or split the mating piece during forcing. The goal is a snug slip fit — the mating piece should slide in with hand pressure but without wobbling. Because sheet goods like plywood are often slightly undersized (a "3/4 inch" sheet is typically 23/32 inch), always measure your actual material and use that measurement as the target groove width rather than the nominal dimension. This is where precise control over blade width per pass becomes especially valuable.