Tenon Size Calculator
Tenon size starts with stock thickness, member width, shoulder allowance and finished tenon thickness. The working calculator then reports cheek cuts and matching mortise allowances.
Tenon ratio
The calculator reports tenon thickness as a percentage of stock thickness so aggressive or thin layouts are visible.
tenon_ratio = tenon_thickness / stock_thickness
Shoulders and width
Finished tenon width is the member width minus equal shoulders on both sides.
tenon_width = member_width - 2 * shoulder_width
Fit allowances
Use the mortise clearance inputs to carry the selected tenon size into a practical fit, then verify with test cuts on the same stock.
Frequently asked questions
How thick should a tenon be?
A common first-pass layout is around one third of stock thickness, but the calculator leaves the final value explicit for your stock and joint style.
Does it include bottom clearance?
Yes. The working calculator includes cheek-side, end and bottom clearance inputs for the matching mortise.
Related pages
- Mortise and tenon calculator - working tenon and mortise layout calculator.
- Mortise tenon calculator - shorter search path for the same workflow.
- Dado calculator - slot sizing for cabinet shelves and dividers.
- Wood movement calculator - movement clearance context before final fitting.