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Woodworking Math

Through dovetail joint

In a through dovetail the pins and tails both run the full thickness of the boards, so the end grain of each shows on the outside of the corner. It is used where the joinery is meant to be seen, on boxes, chests and case corners.

Laying it out

Dovetails are traditionally cut at 1:6 in softwood and 1:8 in hardwood.

Set a marking gauge to the thickness of each board and scribe a baseline around the other board’s end: that line is the depth of the pins and tails. Mark the half pins at the two edges first, then space the tails across the rest of the width. Every width is easiest to work out on the outside face of the pin board, where the pins are narrowest. Across the thickness, each sloped side moves the board thickness divided by r for a 1:r slope, so a tail that is 1 5/8 in wide on the outside of a 3/4 in board at 1:6 is 1/4 in narrower on the inside.

Traditional rule, stated by Fine Woodworking (Taunton Press), Lee Valley Tools and Rockler

Tails or pins first

Whichever part is cut first becomes the template for the second: the second is marked directly from the first rather than measured, so small errors in spacing don’t matter, because the two parts still match each other. Cutting the tails first is a common order, since their slopes are laid out on the face where they are easy to see.

Cutting and fitting

Saw on the waste side of each line down to the baseline, remove the waste with a coping saw or by chopping from both faces with a chisel, and pare to the line. A router jig cuts both parts at once on many models. Test the fit dry; a joint that has to be forced can split the board.

Related joints

Sources

  1. Rockler, Woodworking furniture joinery: butt joints, mortise and tenon, dovetails, read 2026-11-07
  2. Fine Woodworking (Taunton Press), Chris Gochnour, "Laying Out Dovetails", Fine Woodworking #190 (2007), read 2026-11-07
  3. Lee Valley Tools, Veritas Dovetail Markers (1:6 softwood, 1:8 hardwood), product 73357, read 2026-11-07
  4. Rockler, Rockler Dovetail Saddle Squares (1:6 and 1:8), read 2026-11-07

Proportions marked as a traditional rule are shop tradition, not measurements. This site gives no joint-strength numbers: the published tests each used a different rig. How we source these numbers.