What dovetail ratio should I use?

A 1 to 6 slope, about 9.5 degrees, suits softwoods like pine because the steeper angle resists pull-apart in the weaker fibres. A 1 to 8 slope, about 7.1 degrees, looks more refined and works well in hardwoods. Many makers simply pick the look they like, since both hold strongly when cut accurately.

How is the dovetail angle calculated?

The slope ratio 1 to N is rise over run, so the angle from the vertical is the arctangent of one divided by N. A 1 to 6 ratio gives arctan of one sixth, which is about 9.46 degrees, and a 1 to 8 ratio gives about 7.13 degrees.

Does the angle change with board thickness?

No, the angle is fixed by the ratio alone. Thickness only affects how far the angled line travels across the face, which the tool reports as the side offset. A thicker board simply means a longer sloped cut at the same angle.

How many tails should I use?

There is no fixed rule. Narrow drawer sides often use two or three tails, while wide carcass boards may use five or more. As a guide, keep pins narrower than tails for a traditional look, and make sure the half-pins at the edges are stout enough to resist splitting.

Can I use this for both through and half-blind dovetails?

Yes for the angle and the face layout, since both joints use the same slope and tail spacing on the show face. Half-blind joints differ only in how deep you cut the sockets, which is set by the receiving board thickness rather than by this layout.

Dovetail Angle & Layout Calculator

The dovetail is prized for one reason: its angled tails mechanically lock into the pins so the joint cannot pull apart in the direction it is loaded. Getting that lock right starts with a consistent slope angle and an even, deliberate layout, both of which this calculator produces from a couple of numbers.

How it works

Dovetail slope is traditionally written as a ratio of 1 to N, meaning one unit of rise for every N units of run. Converting that to an angle you can set on a bevel gauge is a single trigonometric step.

angle  = atan(1 / N)            degrees from vertical
offset = thickness / N          how far the line travels across the face

A 1 to 6 ratio gives about 9.46 degrees and a 1 to 8 ratio about 7.13 degrees. For layout, the tool places a half-pin at each edge, then divides the remaining width into equal tails separated by interior pins, and draws the result to scale so you can mark straight from it.

Tips, example, and notes

Suppose a 150 mm wide, 18 mm thick pine drawer side with three tails at a 1 to 6 slope and 6 mm half-pins. The bevel angle comes out near 9.5 degrees, the sloped line shifts 3 mm across the 18 mm thickness, and the tails space evenly between the edges.

Set the calculated angle on a sliding bevel or use a dedicated dovetail marker, scribe your baseline at the receiving board thickness, and transfer the tail spacing from the diagram. Cut the tails first, then use them to scribe the pins for a perfect match. Keep the half-pins at the edges substantial so they do not split when the joint is knocked together.