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Enter your stock thickness and the joint's length, then press Calculate.
From the book — Chapter 5. One-third rule: tenon thickness and dado depth = stock ÷ 3 (the other common rule is stock ÷ 2, shown alongside). Side-grain glue area = 2 × depth × length. Face-grain area = stock × length.
The 1/3 rule is the chapter's Rule of Thumb; the 1/2 rule is the common alternative for rabbets. Everything stays in your browser — no sign-up, nothing stored.