Mortise and Tenon Calculator

Inputs

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Thickness through the tenon cheeks.
in
Width across the tenon face before subtracting shoulders.
in
Finished tenon thickness after cheek cuts. A common starting point is around one third of the stock thickness.
in
Shoulder left on each end of the tenon face. Tenon width is member width minus two shoulders.
in
Tenon length entering the mortise before bottom clearance.
in
Mortise width allowance on each tenon cheek.
in
Mortise length allowance at each end of the tenon width.
in
Extra mortise depth beyond finished tenon length for glue and tool-bottom allowance.
in

Results

Default result
Edit inputs
Tenon thickness ratio(t_t/T)
33.33%
Pass

finished tenon thickness divided by stock thickness

Also computed

Cheek cut depth each side(d_c)Pass0.25in

(stock thickness - tenon thickness) / 2

Finished tenon width(W_t)Pass2.5in

member width minus two shoulders

Shoulder width each side(S)Pass0.25in

Shoulder coverage(2S/W)16.67%

Mortise width(W_m)Pass0.256in

tenon thickness plus total cheek clearance

Mortise length(L_m)2.53in

tenon width plus end clearance

Mortise and tenon layout previewMortise and tenon layout previewFinished tenon geometry drives mortise width, length and depth allowances.shoulderstenon widthcheek cutsmortise pocketTenon2.50 in wideMortise0.256 x 2.53 inCheek cut0.250 in
Method notes 6 notes
  • Tenon width = member width - 2 x shoulder width.
  • Cheek cut depth each side = (stock thickness - tenon thickness) / 2.
  • Mortise width = tenon thickness + 2 x side clearance.
  • Mortise length = tenon width + 2 x end clearance.
  • Mortise depth = tenon length + bottom clearance.
  • This is a layout screen only. It does not model joint strength, racking, wood species, grain runout, glue chemistry, shrinkage, tool deflection, haunches, wedges, drawbore pins or frame-and-panel movement.

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