Dovetail Layout & Tail Count Calculator
Enter your finished stock dimensions and the proportions you want. The calculator chooses the valid equal-tail layout closest to that preference, then lists the end-grain and baseline marks for every tail.
Recommended number of tails4
- Wide tail width
- 1.125
- Tail width at baseline
- 0.9583
- Full pin width at baseline
- 0.5417
- Edge half-pin width at baseline
- 0.2708
- Dovetail angle
- 9.46
- End-grain marking schedule
- Tail 1: 0.1875–1.3125; Tail 2: 1.6875–2.8125; Tail 3: 3.1875–4.3125; Tail 4: 4.6875–5.8125
- Baseline marking schedule
- Tail 1: 0.2708–1.2292; Tail 2: 1.7708–2.7292; Tail 3: 3.2708–4.2292; Tail 4: 4.7708–5.7292
Tail cut-line coordinates, measured from the left edge
| Tail | End-grain start | End-grain end | Baseline start | Baseline end |
|---|---|---|---|---|
| 1 | 0.1875 | 1.3125 | 0.2708 | 1.2292 |
| 2 | 1.6875 | 2.8125 | 1.7708 | 2.7292 |
| 3 | 3.1875 | 4.3125 | 3.2708 | 4.2292 |
| 4 | 4.6875 | 5.8125 | 4.7708 | 5.7292 |
All dimensions retain the unit used for the board width. Coordinates are displayed to four decimal places; round to a practical shop increment before marking.
How to use this calculator
- Measure the finished board width and thickness, using either inches or millimetres consistently.
- Choose the approximate wide tail, full pin, and edge half-pin widths you want to see on the end grain.
- Select the dovetail slope that suits the wood and the look of the joint.
- Review the recommended tail count, then mark the listed coordinates from one left-hand reference edge.
- Lay out and cut a scrap sample before transferring the schedule to finished parts.
How the dovetail layout is calculated
A through-dovetail row has equal tails, a full pin between each neighboring pair of tails, and an edge half-pin at each outside edge. This calculator starts from proportions you choose and tries every whole tail count from one through 20. It keeps only layouts with a positive tail at both the wide end and the baseline, then recommends the count whose wide-tail width is closest to your preference. If two counts are equally close, it chooses the smaller count.
Let W be board width, P full-pin width, H edge half-pin width, and N the tail count. The wide tail width is:
T = [W − (N − 1)P − 2H] ÷ N
The two edge half-pins are intentionally independent inputs. Setting each to half of P gives the familiar symmetric layout, but a wider edge allowance can protect a corner or simply suit the look of the work.
Why the baseline marks move
For a slope of 1:r, each sloping line moves sideways by q = B ÷ r across stock thickness B. The tail narrows by that offset on both sides:
baseline tail width = T − 2q
Conversely, a full pin widens to P + 2q at the baseline, and an edge half-pin widens to H + q. The angle shown is atan(1 ÷ r) × 180 ÷ π. For tail i, the end-grain marks are start = H + (i − 1)(T + P) and end = start + T; the baseline marks are those same coordinates moved inward by q.
What changes the layout most
Board width and the preferred tail width drive the recommended count. Larger full pins or wider edge half-pins leave less room for every tail, while thicker stock or a steeper 1:5 slope makes the baseline tail neck narrower. A 1:6 slope is about 9.46 degrees; a 1:8 slope is about 7.13 degrees. Neither ratio guarantees joint strength, because wood species, grain direction, stock condition, and workmanship also matter.
What this calculator leaves out
This is an equal through-dovetail layout only. It does not calculate half-blind socket depth, secret miters, graduated tails, saw kerf, knife-line width, mating-board thickness, or clearance for final flushing. Keep all dimensions in one unit system, choose a sensible marking increment for your tools, and confirm the schedule on offcuts before cutting the workpiece.
Worked example
For a 6 inch-wide, 1/2 inch-thick board with 3/8 inch full pins, 3/16 inch edge half-pins, a preferred 1 inch tail, and a 1:6 slope, the calculator recommends four tails. The wide tail is [6 − (4 − 1) × 0.375 − 2 × 0.1875] ÷ 4 = 1.125 inches.
The slope offset is 0.5 ÷ 6 = 0.0833 inch, so each tail is about 0.9583 inch at the baseline. Tail 1 runs from 0.1875 to 1.3125 inches on the end grain and from about 0.2708 to 1.2292 inches at the baseline. The other tails use the same 1.5 inch end-grain pitch.
Common questions
How many dovetails should a drawer side have?
There is no fixed number. Choose proportions that fit the board width, material, and visual style, then make a sample. This calculator compares one through 20 equal-tail arrangements and picks the valid count closest to the wide-tail width you prefer.
What is the difference between 1:6 and 1:8 dovetails?
A 1:6 slope is steeper, at about 9.46 degrees, while 1:8 is shallower, at about 7.13 degrees. The steeper slope produces more sideways movement over the same stock thickness and therefore a narrower tail at the baseline. Ratio choice is partly a visual and material-specific decision, not a strength rating by itself.
How wide should dovetail pins and half-pins be?
Use a full-pin width that you can saw and pare accurately and an edge half-pin that leaves a durable corner. The conventional equal layout uses half-pins equal to half the full-pin width, but they can be wider when the appearance or corner strength calls for it. Enter the actual widths you want rather than relying on a fixed rule.
Why are tail widths different at the end and baseline?
The tail sides are angled, so each line moves inward as it travels from the end grain to the baseline. The amount of movement is stock thickness divided by the second number in the slope ratio. Both sides move, so the baseline tail is narrower by twice that offset.
Can the layout be transferred with dividers instead of a ruler?
Yes. After checking the schedule, set dividers to the repeated end-grain pitch of wide tail plus full pin and step it from a marked edge half-pin. Still knife or pencil the individual boundaries carefully, and verify that the final edge lands where the schedule predicts before sawing.