WoodCalcs.uk
Biscuit Joint Calculator — Biscuit Size and Spacing
Calculate biscuit size, quantity, and spacing for panel and edge joints.
How We Calculate This
This calculator determines biscuit quantity and spacing for your joint.
Spacing rules
- Edge distance: minimum 75mm from each end
- Target spacing: ~150mm between biscuits
- Minimum 2 biscuits per joint
Slot depth
Slot depth = half the biscuit width + ~1mm clearance for glue expansion (e.g. #20 = 23/2 + ~1 ≈ 12.5mm, matching Lamello’s 12.3mm). The biscuit’s length runs along the joint line; only its width penetrates the board edge.
Frequently Asked Questions
Use the largest biscuit that fits your stock thickness. #20 biscuits for 18mm+ stock, #10 for 15mm+ stock, and #0 for 12mm+ stock. Larger biscuits provide better alignment and more glue surface.
Space biscuits 100–200mm apart for edge joints, with 150mm being the most common spacing. Keep at least 75mm from each end. For mitre joints, use one biscuit every 150mm.
Biscuits add some strength and significant alignment benefits. In edge-to-edge joints, the glue bond is already stronger than the wood. Biscuits are most valuable for keeping boards aligned during clamping and for adding strength to mitre joints.
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Last updated: February 2026
All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.