Joinery
Biscuit Joint Quantity Calculator
Figure out how many #0, #10, or #20 biscuits you need for a glue-up — by joint length and biscuit spacing rules.
Calculator
Default 6 in for #20, 4 in for #10.
What makes this different
Most biscuit calculators assume 6 in spacing for #20 biscuits. This one lets you tune the spacing by stock thickness and joint type, and tells you which biscuit size (0/10/20) fits your stock.
Who it's for & when to use it
Edge-to-edge panels, mitered boxes, face frame assembly.
How to use
- Enter the dimensions of your material or the parameters of your project.
- Adjust the optional knobs (waste factor, kerf, planer allowance) to match your shop practice.
- Click Calculate and read the output. Use the per-item breakdown for ordering, the totals for budgeting.
- Compare the result to your lumber yard's quote — the effective $/BF column is the apples-to-apples number.
Formula: Count = floor(joint_len / spacing). Adjust spacing down for hardwood and thin stock.
Notes & tips from the shop
- #0 for thin stock (< 1/2 in), #10 for 1/2–3/4 in, #20 for 3/4 in and up.
- Biscuits swell on contact with glue — they pull the joint tight. Don't soak them.
- Always align the factory edges (or run them through a jointer) so the biscuit slot references a flat surface.
Frequently asked questions
Why is my biscuit not flush?
Likely the slot depth is set wrong. The slot should be exactly biscuit length minus 1 mm so the biscuit is fully seated when flush.
Can I use biscuits for structural joints?
No — biscuits are alignment aids, not structural fasteners. For load-bearing joints, use mortise & tenon or dominoes.
How do I stop the biscuit from spinning in the slot?
Use a dry biscuit; glue moisture will swell it within seconds and lock it in place.
Limitations
Single-row biscuits only. Domino loose tenons follow a different sizing chart.
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