MachineCalcs

Dovetail Spacing Calculator

Lay out equal-spaced woodworking dovetail tails and pins from board width, tail count, pin-to-tail ratio, board thickness, wood species and dovetail angle.

Materials 7 inputs 13 results
Used in Woodworking 25

Calculator

Inputs

View results
Width across the dovetail layout.
in
Thickness used to estimate the angled side offset.
in
Optional slope guide. Common shop convention uses steeper 1:6 slopes for softwoods and shallower 1:8 slopes for many hardwoods.
Number of full tails across the board. Edge pins are treated as half pins.
tails
Full pin width divided by full tail width.
Slope is expressed as rise:run across the dovetail side. 1:6 is steeper than 1:8.

Results

Default result
Edit inputs
Full tail width(T_w)
0.6897in
Pass

4 full tails.

Also computed

Full pin width(P_w)Pass0.3103in

Full pin width; edge pins are half this.

Edge half-pin width(P_e)0.1552in

Tail layout pitch(p)1in

One full tail plus one full pin width.

Side offset through thickness(o)0.125in

From 1:6 slope through the board thickness.

Tail side angle(a)9.462°

Slope 1:6.

Slope denominator(x)6for 1:x

Equivalent slope 1:6.

Dovetail layout across board width board width divided into 4 equal pitches T1 T2 T3 T4 Edge pins are half of the full pin width; internal pins use the full pin width. Guidance: recommended slope 1:6; max cleanup chisel 0.264 in.
Method notes 5 notes
  • Layout assumes equal-width tails, equal full pins, and two edge half-pins that together equal one full pin.
  • Formula: tail width = board width / (tail count x (1 + pin-to-tail ratio)); pin width = ratio x tail width.
  • Species slope guide: Eastern white pine maps to 1:6. Use it as a starting convention, not a rule.
  • Max cleanup chisel width is a practical screen for clearing the narrowest full pin/tail gap; pick the next smaller chisel in your rack.
  • This is a marking and spacing aid only. It does not account for saw kerf, paring allowance, wood movement, grain, glue clearance, joint strength or left/right board orientation.

Dovetail spacing starts by treating the two edge half-pins as one full pin width. With N tails and pin-to-tail ratio r, board width is W = N*tail + N*pin and pin = r*tail, so tail width = W/(N*(1+r)). This calculator returns full tail width, full pin width, edge half-pins, pitch, dovetail angle, side offset through the board thickness, a species-based slope guide and a cleanup-chisel width screen.

Continue workflow

All Materials
Workflow placement Woodworking Stage 3: Check behavior and finish
Next 1 Size drawer box Size the drawer box first so drawer side width, height and thickness are known before joinery layout. Next 2 Build cut list Pack drawer sides, rails or case parts into stock boards before laying out joinery. Next 3 Check wood movement Check seasonal movement before choosing tight pin gaps or reveal-sensitive layouts. Chart Use reference data Decimal to fraction chart

How to use this calculator

  1. Enter board size. Use the board width across the dovetail layout and the board thickness through the joint.
  2. Pick wood species. Use the species selector for a starting slope convention.
  3. Pick tail count. Choose the number of full tails you want across the board.
  4. Set pin ratio. Enter the full pin width as a ratio of the full tail width.
  5. Choose slope. Use 1:6, 1:7, 1:8 or a custom angle, then mark full tails, full pins and edge half-pins from the results.
  6. Check tools. Use the cleanup chisel width as a quick check against the narrowest full pin or tail space.

How it works

The calculator treats the layout as repeated tail-plus-pin pitches. For N full tails and pin-to-tail ratio r, the two edge half-pins count as one full pin width, so the width equation is:

W = N x tail width + N x pin width

Since pin width = r x tail width, the solved widths are:

tail width = W / (N x (1 + r))

pin width = r x tail width

The side offset through the board thickness is a simple angle relation:

offset = thickness x tan(angle)

The species selector does not change the selected layout angle. It adds a starting guide: softwood presets map to a steeper 1:6 slope, most hardwood presets map to a shallower 1:8 slope, and custom stock maps to 1:7. The cleanup-chisel result is 85% of the smaller full pin/tail width so the tool fits inside the narrowest space with room for paring.

Dovetail marking sequence
Step Use this result Shop note
Edge half-pins Edge half-pin width Mark both board edges before stepping the pitch.
Repeat spacing Tail layout pitch Step each full tail plus full pin interval across the board.
Side lines Side offset through thickness Transfer the slope through the board thickness before sawing.
Cleanup tool Max cleanup chisel Pick the next smaller chisel; paring allowance is still shop-specific.

Worked example

Verified against the live calculator

For a 4 in wide board, 3/4 in thickness, 4 tails, a 0.45 pin-to-tail ratio and a 1:6 dovetail slope, the layout pitch is exactly 1.00 in. Each full tail is about 0.690 in, each full pin is about 0.310 in, each edge half-pin is about 0.155 in, and the side offset through the thickness is 0.125 in. For an eastern white pine preset, the species guide stays at 1:6, and the cleanup chisel screen is about 0.264 in, so a 1/4 in chisel is the nearest common smaller choice.

Frequently asked questions

How do you space dovetails evenly?

Choose a tail count and a pin-to-tail width ratio. This calculator treats the two edge half-pins as one full pin, then divides board width into equal tail-plus-pin pitches.

What does a 1:6 dovetail slope mean?

A 1:6 slope means the dovetail side moves 1 unit sideways for every 6 units of run. As an angle from square, that is about 9.46 degrees.

Should I use 1:6 or 1:8 dovetails?

A common shop convention is 1:6 for many softwoods and 1:8 for many hardwoods. The calculator shows a species-based guide, but the final choice still depends on style, tools, grain and stock quality.

How wide should my cleanup chisel be?

Use a chisel narrower than the smallest full pin or tail space. The max cleanup chisel output uses about 85% of the smaller full pin/tail width as a practical upper bound.

Does this account for saw kerf or chisel cleanup?

No. It gives finished layout widths. Mark from a knife line and leave whatever sawing or paring allowance your workflow requires.

Method & assumptions

  • Layout assumes equal full tails and equal full pins across the board.
  • The two edge pins are half-pins; together they equal one full pin width.
  • Angle presets use simple slope geometry: 1:6, 1:7 or 1:8. Species guidance is a starting convention, not a strength rule.
  • Max cleanup chisel width is based on the smaller full pin/tail width, before saw kerf or paring allowance.
  • The SVG and marking table are print-friendly layout aids, not 1:1 templates with tool compensation.
  • Does not include saw kerf, chisel paring allowance, glue clearance, wood movement, grain direction, joint strength or handed board orientation.
  • For adjacent woodworking planning, use the cut list calculator, board feet calculator and wood movement calculator.
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