Dovetails look hand-cut and perfect only when the layout is right — the angle, the tail widths and the spacing all come from your board, not from guesswork. Enter your board below and this calculator gives you the dovetail angle, the exact tail and pin widths at the baseline and the top, and the marking positions along the edge.
Your board
How the math works
The dovetail slope is a ratio — 1:6 for hardwood, 1:8 for softwood. The angle is the arctangent of that ratio, and the sideways offset at the top of the board is the thickness divided by the ratio:
Angle = arctan(1 ÷ ratio) — 1:6 is 9.46°, 1:8 is 7.13°
Slope offset per side = thickness ÷ ratio
Tail width at baseline = (board width − (tails − 1) × pin width − 2 × half-pin) ÷ tails
Tail width at top = tail baseline − 2 × offset · Pin width at top = pin width + 2 × offset
Worked example: a 12″ wide, ¾″ thick hardwood board with 5 tails and ⅜″ pins at a 1:6 slope gives an angle of 9.46°, a slope offset of 0.13″ per side, and a tail width of 2.03″ at the baseline (2.03″ = (12 − 4 × 0.375 − 2 × 0.1875) ÷ 5). The tails narrow to 1.78″ at the top while the pins widen to 0.63″.
Tips for clean dovetails
- Cut the tails first, then mark the pins from them. Use the cut tails themselves as the template — the pins will match the tails exactly, whatever small errors crept in.
- Mark with a knife, not a pencil. A knife line is a precise cut you can register a chisel in; a pencil line is a suggestion. See the FAQs below for the full comparison.
- Keep the pins narrow, the tails wide. Pins carry the strength across the grain, so they should be slim (about ⅜″ at the baseline); tails are mostly show, so let them be wide.
- Angle the saw, not the board. Saw just to the waste side of the knife line and pare to it with a chisel — a saw cut on the line itself is a gap you cannot close.
- Practice on a small box first. A wooden jewelry box is the classic first dovetail project — small boards, forgiving proportions, and a useful result.
Frequently asked questions
Should I use a 1:6 or 1:8 dovetail angle?
Use 1:6 (about 9.5°) for hardwood and 1:8 (about 7.1°) for softwood. Hardwood is strong enough across the grain to hold a steeper, more mechanical angle; softwood is weaker, so a gentler slope leaves more long grain in the pins and resists splitting. The calculator above uses the right ratio for the wood you pick.
How many tails should a dovetail joint have?
As a rule of thumb, aim for tails roughly 1″ to 2″ wide at the baseline. Divide your board width by that range: a 6″ drawer side wants 3–4 tails, a 12″ board wants 5–6. More, narrower tails look fussy and are harder to cut cleanly; fewer, wider tails look clumsy and waste the joint’s strength.
What is the difference between half-blind and through dovetails?
Through dovetails show the joint on both faces and are the strongest — the classic choice for boxes and carcases. Half-blind dovetails hide the joint from the front, so they are used on drawer fronts, where you want a clean face with the joint visible only from the side. The layout math is the same; only the depth of the cut differs.
Should I mark dovetails with a marking knife or a pencil?
A marking knife, always, for the layout lines. A knife severs the wood fibres and gives you a crisp line to register a chisel against, so your cuts land exactly on the line. A pencil line is wider than a saw kerf and rubs off mid-cut. Use a pencil only for rough notes and waste-side marks (an “X” in the waste is a good habit).