Dado Blade Width Calculator
Compute the per-pass blade width to set on your saw when cutting a dado that requires multiple passes to reach the target groove width. Useful when your dado stack does not match the target width exactly, or when using a standard blade to make a dado in several passes.
Last updated: May 2026
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About this calculator
A dado is a flat-bottomed groove cut across the grain of a board, used for shelves, drawer bottoms, and cabinet backs. The formula is bladeWidthPerPass = desiredWidth / numberOfPasses. Variables: desiredWidth is the final target groove width in inches (typically matching the thickness of the panel that will fit into it — usually 1/4 inch, 1/2 inch, 3/4 inch, or 13/16 inch); numberOfPasses is how many cuts you plan to make across the same groove to achieve the desired width. Edge cases: with a dedicated dado stack (a set of two outer blades and various chippers and shims), most groove widths can be achieved in a single pass — set the stack to the target width and cut once. The multiple-passes approach is needed when (1) you don't have a dado stack and must use a standard kerf blade, (2) the target width exceeds the maximum width of your dado stack (typically 13/16 inch on home-shop table saws), or (3) you want a smoother bottom than a chipper-based dado produces. In multi-pass cutting, position the fence for the first pass, make the cut, then shift the fence by exactly the bladeWidthPerPass and make the next cut, repeating until you've completed numberOfPasses cuts that together produce the full desired width. The formula assumes the blade kerf is exactly bladeWidthPerPass; in practice, the blade kerf is fixed by the blade you own (typically 1/8 inch for thin-kerf or 3/16 inch for full-kerf table saw blades), so the number of passes adjusts to the formula desired / kerf rounded up to a whole number, and the fence shift adjusts to (desired − N × kerf) / (N − 1) or similar partial-overlap math. Plywood thickness considerations: nominal 3/4″ plywood is typically 23/32 inch in actuality, so target the actual thickness, not the nominal — a 3/4-inch dado will not snugly fit modern plywood.
How to use
Example 1 — 3/4-inch dado for plywood shelf. Desired width 23/32 inch (the actual thickness of '3/4 inch' plywood), planning 3 passes with a 1/4-inch-kerf blade. Step 1: bladeWidthPerPass = 23/32 / 3 = 0.241 inch per pass. Step 2: with a 1/4-inch (0.25-inch) blade, this means each pass nearly fully replaces the previous cut with minimal overlap — really requiring only 3 passes if you nudge the fence by 0.241 inch between each. Step 3: in practice, make pass 1 with fence at position A; make pass 2 with fence at A + 0.241; make pass 3 with fence at A + 0.482. Verify total width: 0.482 + 0.25 = 0.732 inch = 23/32 inch ✓. Example 2 — 1/4-inch groove with a standard kerf 1/8-inch blade. Desired width 1/4 inch (0.25 inch), planning 2 passes. Step 1: bladeWidthPerPass = 0.25 / 2 = 0.125 inch per pass. Step 2: each pass is exactly the blade kerf (1/8 inch). Step 3: pass 1 at fence position A; shift fence by 0.125 inch; pass 2 at A + 0.125 inch. Verify: each cut removes the blade kerf, and the two side-by-side cuts together produce a 0.250 inch wide groove with a flat bottom. This is the simplest multi-pass dado scenario — use it when no dado stack is available.
Frequently asked questions
When do I need a dado stack versus making multiple passes with a standard blade?
Use a dado stack (multi-blade adjustable set) when you cut dadoes regularly — it produces a clean flat-bottomed groove in a single pass and saves significant time. A typical dado stack costs $80–$300 and can produce groove widths from 1/4 inch (just the two outer blades) to 13/16 inch (outers plus all chippers and shims) in 1/16-inch increments. Multiple-pass cuts with a standard blade are appropriate when you make occasional dadoes, don't own a dado stack, need a groove wider than 13/16 inch (most dado stacks max out there), or want a marginally smoother bottom than chipper cuts produce. Multiple-pass downsides: each pass adds setup time (positioning the fence accurately) and risks misalignment that produces a stepped, non-flat bottom. Modern alternatives include using a router with a straight bit (very clean, but slow and requires a router table or edge guide), a router with a top-bearing bit and template (cleanest result, more setup), or specialty dado jigs for handheld circular saws (rough cut, suitable for utility work). For a one-off project, multiple passes work; for a kitchen full of cabinets, invest in the dado stack.
What is the difference between a dado, a groove, and a rabbet?
All three are flat-bottomed channels cut into wood for joinery, but they differ in orientation and shape. A dado is a groove cut across the grain (perpendicular to the long fiber direction) — typical use: shelves locked into the sides of a bookcase. A groove is the same kind of channel but cut with the grain (parallel to fibers) — typical use: panel bottoms in drawer sides, or back panels in cabinets. A rabbet is a step cut along the edge or end of a board, removing only one shoulder — typical use: case joinery at the back of a cabinet, or fitting a window pane into a frame. All three use similar cutting setups (dado stack, multi-pass on table saw, router with straight bit, etc.), and the formula bladeWidthPerPass = desiredWidth / numberOfPasses applies to all of them. A dado that runs partway across a board (stops before reaching one edge) is called a stopped dado or blind dado, requiring different cutting techniques because you can't approach with a saw from both ends. Half-blind and through-dovetails use angled rather than perpendicular sides.
How do I ensure a snug-fitting dado with no slop and no force-fit?
A well-fitting dado allows the mating piece to slide in with firm hand pressure, without wobble and without needing a mallet. The mating-piece thickness must match the dado width exactly. For plywood: modern 'nominal 3/4 inch' plywood is actually 23/32 inch (0.719 inch), and '1/2 inch' plywood is 15/32 inch (0.469 inch) — measure your actual material with calipers before cutting the dado. Some plywood is even 19/32 or 21/32 inch depending on the manufacturer. Set the dado width 0.001–0.005 inch wider than measured stock for a slip-fit, or exactly matching for a friction-fit (the latter is preferred for glued joinery as glue thickness fills the small gap). Test your setup on scrap of the exact same material as your workpiece before cutting the final dado. If your test fit is too tight, make a partial test pass to widen the dado slightly; if too loose, you must start over with a fresh setup. Solid wood mating pieces should be milled to thickness with a planer, then test-fit. For joinery requiring expansion clearance (panels that need to move seasonally), make the dado 1/32 inch deeper than the panel thickness and use elongated screw slots or no glue.
What are common mistakes when planning and cutting dadoes?
The most common mistake is targeting nominal '3/4 inch' or '1/2 inch' dimensions when actual plywood is 23/32 or 15/32 inch — produces sloppy dadoes. Setting up the dado stack without test cuts on scrap leads to over-wide grooves (no rework available). On multi-pass cuts, failing to shift the fence by exactly the calculated bladeWidthPerPass between passes produces a non-flat bottom with ridges where overlapping cuts meet at different depths. Cutting dadoes across narrow stock (less than 6 inches wide) without a miter gauge or sled is dangerous and inaccurate — the workpiece can rotate or kick back. Using a dado stack on a saw whose throat plate doesn't accept a wider blade or whose motor is underpowered (less than 1.5 HP) leads to bogging down and burning. Cutting through-dadoes (open on both ends) when you wanted stopped dadoes (closed at one end) is a design vs. fabrication confusion. Forgetting to support the workpiece beyond the saw table on long boards leads to wandering cuts. Dadoes cut into MDF or particleboard need a clean-cutting blade with low chip-out; standard table-saw blades produce ragged edges. Finally, not allowing for sawdust accumulation at the bottom of a deep dado can prevent the mating piece from seating fully — vacuum or brush out before final assembly.
When should I NOT use this calculator?
Skip the bladeWidthPerPass formula when using a dedicated dado stack set to the exact target width in one pass — no multi-pass math needed. Do not use it for through-dovetails, half-blind dovetails, mortise-and-tenon joinery, or other shaped joints with non-rectangular profiles — those have their own geometry. Avoid it for stopped dadoes where the cut doesn't go through the full board — you may need to plunge with a router or stop short with the table saw and clean up with a chisel. The formula does not work for sliding dovetails or any tapered/angled grooves; those use router bits with specific angle profiles. For curved or arched dadoes (decorative case sides, sweeping shelves), use a router with a template rather than a table saw. The formula doesn't apply to half-laps and bridle joints which are typically cut at one specific width matched to mating stock thickness. For mortises, use a hollow-chisel mortiser or a router with a plunge base, not table saw passes. For very deep dadoes (more than 1.5× the blade kerf), multiple cuts at progressively deeper depths are needed regardless of width, complicating the formula. Finally, for any dado in dimensional lumber that hasn't been jointed flat first, results will be inconsistent across the cut; flatten and square the stock before dadoing.