Turn board dimensions into balanced tails and pins in seconds onsite today. Print or export results to guide layouts, reduce waste, and rework fast.
This calculator uses a balanced spacing model with half pins at both edges.
| Board width | Thickness | Tails | Edge margin | Mode | Ratio | Slope |
|---|---|---|---|---|---|---|
| 180 mm | 18 mm | 5 | 8 mm | Ratio | 2 : 1 | 1:7 |
| 240 mm | 20 mm | 6 | 10 mm | Fix pin | — | 1:8 |
| 150 mm | 15 mm | 4 | 6 mm | Fix tail | — | 1:6 |
Accurate dovetails start with layout, then careful cuts always.
On busy sites, dovetails are often laid out from rough dimensions and a quick ratio guess. That works until pins become too thin, tails become oversized, or the edge half‑pins crack during handling. This tool converts board width, thickness, margins, and a chosen tail count into a balanced spacing plan that can be marked directly from the left edge.
The calculator assumes half pins at both edges because it protects the corners and produces symmetrical spacing. The usable width is the board width minus two edge margins, then the usable width is split into repeating tail and pin segments. This approach keeps the pattern stable even when the tail count changes.
Ratio mode is the quickest way to reach a practical layout. A common tail‑to‑pin ratio is around 2:1 for general joinery, but thinner stock may need a smaller ratio to avoid fragile pins. Because pin width is computed from usable width and the ratio, the pattern remains proportional as boards scale up.
When drawings specify a target pin or tail width, use the fixed modes. Fix‑pin mode is helpful when you already have a router bit or jig spacing. Fix‑tail mode helps match a visual rhythm across multiple casework parts. The calculator checks for negative widths and flags combinations that cannot fit.
Slope presets like 1:6, 1:7, and 1:8 represent the rise‑to‑run relationship of the dovetail wall. A steeper 1:6 creates stronger mechanical lock but increases side offset. A gentler 1:8 looks cleaner and can be easier to fit. The tool converts slope to an angle from vertical for reporting.
With thickness included, the calculator estimates the side offset caused by the chosen slope. Offset equals thickness divided by the run, and it expands the tail at the face while shrinking the pin at the face. If the computed pin face width trends to zero, the results panel warns you to reduce slope steepness or increase pin size.
Kerf settings are presented as an informational allowance so crews can note saw line consumption without distorting the base geometry. For hand cutting, keep the segment widths as the target, then mark two lines per boundary: one for the waste side and one for the finished surface. Consistent marking improves repeatability.
CSV export supports quick sharing with supervisors and fabrication notes, while the PDF summary works for attachment to inspection or close‑out records. Store the segment table with job references and board identifiers so rework can be recreated exactly. Reliable layouts reduce waste, re-cuts, and schedule risk.
Use a margin that protects the corner half pin. A practical range is 5–12 mm for small work, or about 1/4–3/8 in for thicker stock. Increase margin when boards are brittle or heavily handled.
1:7 is a common all‑round choice. Use 1:6 for higher mechanical lock in softwoods, and 1:8 for a cleaner look or when pins risk becoming too narrow. Match the slope to your gauge or jig.
Half pins strengthen the corners and give a symmetrical pattern. They also make the marking process easier because the first boundary starts after the margin and a half‑pin width, reducing corner breakout during cutting and fitting.
It means the chosen pin width cannot fit the selected number of tails within the usable width. Reduce the pin width, reduce the tail count, or increase board width. The tool warns when computed widths are not physically possible.
Not always. Many teams keep the nominal segment widths and control kerf by marking waste sides consistently. Use kerf as a reference for saw line planning and notes, especially when multiple operators cut the same joint type.
The segment table is measured from the left edge, with the margin built into the first start position. This makes field marking straightforward: hook your tape at the edge, mark each start and end, then strike your lines.
Yes, but stay consistent within a single calculation. The units selector affects displayed labels, while the math uses your numeric inputs directly. If you switch units, convert your dimensions before recalculating to avoid mismatched spacing.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.