Last updated: 2026-02-27

Dado Calculator - Dado & Groove Depth, Width & Spacing Guide

Free dado calculator for perfect dado and groove joints. Calculate dado depth, width, and spacing for shelves, cabinets, and drawers. Includes router bit sizing, tolerance calculations, and plywood thickness guide. Determine optimal dado dimensions for tight-fitting joints. Perfect dados every time!

Real-time Calculation Safety Guidelines Joint Strength Multiple Species

Dado Specifications

Calculation Results

Enter dado specifications and click "Calculate Dado Dimensions" to see your joint dimensions and safety guidelines.

Use proper safety equipment. Ensure blade height and fence settings correct. Test on scrap first. Never exceed 50% material thickness.
Calculations are engineering guides. Test fit and adjust based on wood species, tools, and actual material dimensions.

How to Use This Calculator

  1. 1
    Enter Material Thickness Input the thickness of the board receiving the dado cut. This determines the maximum safe depth.
  2. 2
    Set Insert Thickness Enter the actual measured thickness of the piece that will fit into the dado (shelf, divider, panel).
  3. 3
    Select Dado Type Choose: Through Dado (full width), Stopped Dado (hidden front), Rabbet (edge cut), or Groove (with grain).
  4. 4
    Choose Wood Species Select from 7 material types: pine, oak, maple, birch, plywood, MDF, or particleboard. Affects strength calculations.
  5. 5
    Set Fit & Load Choose fit type (snug/tight/loose/glue) and expected load (light to structural). Get optimized depth and width.
Pro Tip: Always measure ACTUAL material thickness — never assume nominal dimensions! Plywood labeled 3/4" is often 0.720" actual. Cut dado to match the real measurement, not the labeled size.

Dado & Groove Joint Types & Applications

Dado vs. Groove: Fundamental Difference

Dado Joint: A rectangular channel cut across the grain (perpendicular to wood fibers). Requires more care to prevent tearout. Provides excellent mechanical strength.

Groove Joint: A rectangular channel cut with the grain (parallel to wood fibers). Easier to cut cleanly and less prone to tearout.

Through Dado

Cut runs completely across the full width. Visible from both edges. Strongest variation, simplest to cut. Ideal for internal construction where edges won't be visible.

Stopped Dado (Blind Dado)

Cut stops before reaching the front edge. The mating piece is notched to accommodate. Clean, professional appearance. 85-90% strength of through dado.

Rabbet Joint

L-shaped channel cut along the edge. Conceals end grain. Versatile for box construction, back panels, and frame corners.

Dado Strength Comparison (3/4' Plywood, 12' Shelf Span, 50 lb Load)
  • Through Dado (3/8" deep): Maximum strength, no deflection, 300+ lb capacity
  • Stopped Dado (3/8" deep): 85-90% strength of through dado
  • No Dado (shelf on cleats): 40-50% strength, significant deflection
  • Conclusion: Dados dramatically increase load capacity and eliminate shelf deflection

Dado Depth, Width & Fit Tolerances

The 50% Rule

Maximum dado depth should never exceed 50% of material thickness. Exceeding this dramatically weakens the material and risks catastrophic failure under load.

Dado Depth Safety Reference
Material ThicknessMaximum DepthRecommended DepthSafety Limit
1/2"1/4"3/16"50% rule
5/8"5/16"1/4"50% rule
3/4"3/8"1/4"-5/16"50% rule
1"1/2"3/8"50% rule
These are general guidelines. Actual safe depth depends on wood species strength, grain orientation, and load requirements.
Dado Width = Insert Thickness + Fit Tolerance
Dado Width for 3/4' Plywood (Actual 0.720')
  • Loose fit (removable): 0.730"-0.735" wide (+0.010"-0.015")
  • Standard fit (glued): 0.722"-0.725" wide (+0.002"-0.005")
  • Tight fit (max strength): 0.720"-0.722" wide (exact to +0.002")

Critical Rule: Always measure ACTUAL material thickness — never assume nominal dimensions!

Cutting Methods: Table Saw vs. Router

Table Saw with Dado Blade Set

Extremely consistent depth, fast for multiple identical dados, excellent for through dados and long grooves. Requires stacked dado blade set ($150-$300) and sufficient saw power (1.5+ HP).

Router with Straight Bit

Perfect for stopped dados with easy start/stop control. Portable, works on assembled pieces. Ideal for curved or angled dados. Multiple passes recommended for depth control.

Table Saw vs. Router: Decision Matrix
ApplicationBest ToolReason
Through Dados, Multiple PiecesTable SawFaster, more consistent
Stopped DadosRouterEasier start/stop control
Assembled PiecesRouterOnly option
Wide Panels (>24")RouterSafer than table saw
Production RunsTable SawMuch faster
Job Site WorkRouterPortable
Tool selection also depends on available equipment, operator experience, and specific project requirements.
Pro Dado Fitting Techniques
  • Test Cut System: Make dado on scrap, test fit mating piece, adjust before cutting actual workpiece
  • Shim Adjustment: If dado is slightly wide, use veneer shims (0.020"-0.040") on mating piece edges
  • Plane to Fit: If mating piece is oversize, use hand plane to reduce thickness incrementally
  • Multiple Passes: Sneak up on final width with multiple light passes rather than one full-depth cut

Glossary of Terms

Dado

A rectangular channel cut across the grain (perpendicular to wood fibers). Provides mechanical housing for shelves and dividers. Named from Italian 'die' — the lower portion of a wall.

Groove

A rectangular channel cut with the grain (parallel to wood fibers). Used for panel construction where the channel runs along the length of frame pieces. Easier than dado to cut cleanly.

Rabbet

An L-shaped channel cut along the edge or end of a board. Removes material from one face. Used for back panels, box corners, and frame construction.

Through Dado

A dado cut that runs the full width of the board, from edge to edge. Visible from both sides. Strongest variation, providing maximum glue surface and mechanical strength.

Stopped Dado

A dado that stops before reaching the front edge. The mating piece is notched to fit. Provides 85-90% of through dado strength with hidden joint appearance.

Dado Blade Set

A stacked blade set for table saws consisting of two outer blades and interchangeable chipper blades. Adjustable from 1/4" to 13/16" width. Quality sets cost $150-$300 (Freud, Forrest, CMT).

50% Rule

The maximum safe depth for a dado is 50% of the material thickness. Exceeding this dramatically weakens the board and risks failure under load. For 3/4" stock: max 3/8" deep.

Fit Tolerance

The clearance between dado width and insert thickness. Snug fit: +0.002". Standard: +0.002-0.005". Loose: +0.010-0.015". Critical for joint strength and assembly ease.

Frequently Asked Questions

What's the maximum safe dado depth?

Generally, dado depth should not exceed 1/2 of the material thickness. For 3/4" stock, maximum depth is 3/8". Deeper cuts significantly weaken the material and may cause failure under load.

How tight should a dado joint fit?

A proper dado joint should fit snugly with hand pressure. If you need a mallet, it's too tight and may split the wood. If it falls in freely, it's too loose for a strong joint.

Should I use glue in dado joints?

For permanent assemblies, use wood glue in the dado. For removable shelves, a snug fit without glue allows for future adjustments. Always consider the intended use.

Can I cut dados in plywood?

Yes, but be careful with depth. Plywood layers can delaminate if cut too deep. Use sharp blades and support the workpiece well to prevent tearout. Never exceed 1/3 thickness for plywood.

What's the difference between a dado and a groove?

A dado runs across the grain, while a groove runs with the grain. Both use similar cutting techniques but grooves are typically easier to cut and less prone to tearout.

How do I prevent dado tearout?

Use sharp blades, score the cut line first, support the workpiece properly, and consider using a sacrificial backing board. Climb cutting can also reduce tearout but requires extra caution.