Boards
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Shop estimate. Measure your stock and cut a test on scrap.
How to use it
- Enter the finished width of the panel.
- Enter the rough width of one board, after you have decided they will match.
- Enter how much width a glue line removes. A light jointing pass is often near 1/32 inch (0.8 mm). Use what your plane actually takes.
- Read the board count. Edge boards and middle boards are already in the formula: n boards make n − 1 glue lines.
The formula
Boards = the smallest n where n × rough width − (n − 1) × joint loss ≥ finished width.
- n − 1. Glue lines between n boards. The two outside edges are not glued to anything.
- Extra. How much wider the glued panel is than the finished width, before you rip it to size.
- Face. Finished width divided by the board count. That is the face of each board after jointing, if you want them equal.
Worked example
A 24 inch top from 5½ inch boards, losing 1/32 inch at each glue line, needs 5 boards. Four boards come out to 21.906 inches, short of 24. Five boards glue up to 27.375 inches, 3.375 inch over the finished width.
Each board then finishes at 4.8 inches of face if you want them equal. The outside edges, if you joint those too, are an extra loss this count does not include.
What it will not decide
- Equal boards only. A mix of widths is a different sum.
- It does not alternate growth rings or bookmatch a flitch.
- Joint loss is whatever you type. It is not a standard pass depth.
Questions
Why can four boards come up short?
Because each joint throws away a shaving. Four boards of 5½ inches with a 1/32 inch loss at each of three joints are under 22 inches, not 22 inches exactly. The worked example is a 24 inch top that needs a fifth board.
Should the outside edges be jointed too?
Usually yes, and then ripped to the panel. That loss is not in the glue-line count. If you joint the outside edges as well, add two more losses yourself or start with a slightly wider finished number.
Does this include the thickness?
No. Thickness is a separate board-foot question. This page is only the width of the panel.