Biscuit Joint Sizes (No. 0, 10, 20): Dimensions and Applications Compared

September 13, 2025

A biscuit joint, often referred to in joinery by the original inventor's name Lamello, is an oval connecting plate made of compressed beech wood. Standard sizes 0, 10, and 20 differ in length and width, but all feature a standardised thickness of 4 mm. They are used for form-fitting construction in engineered wood and timber.

What Exactly Is a Biscuit Joint?

A biscuit joint is a core component in modern jointing techniques for furniture construction. To use these plates, a dedicated biscuit jointer is used to cut an exact 4 mm wide slot into the workpieces being joined.

The principle of stability relies on a material reaction: just like a dry sponge absorbing water, the highly compressed beech wood reacts to the moisture in the applied wood glue. The plate swells inside the routed groove and wedges tightly in a form-fitting manner. The result is a heavy-duty, invisible timber joint that prevents components from slipping sideways whilst the glue sets.

Biscuit Joint Sizes: Comparing Dimensions and Standards

The geometry of these connectors is standardised across the entire industry. Regardless of the manufacturer, all classic biscuit joints feature an exact material thickness of 4 mm. The distinction between sizes 0, 10, and 20 relates solely to length, width, and the resulting cutting depth.

Size 0

This variant is the smallest of the three standard sizes and is primarily used for delicate frame joints or very thin materials.

Length x width: 47 x 15 mm
Thickness: 4 mm
Required cutting depth: 8 mm
Recommended board thickness: 8 mm - 12 mm

Size 10

The medium dimension provides the ideal compromise for components that are too solid for the smallest size, yet too narrow for the largest.

Length x width: 53 x 19 mm
Thickness: 4 mm
Required cutting depth: 10 mm
Recommended board thickness: 12 mm - 15 mm

Size 20

This is the absolute standard dimension in traditional furniture and interior joinery. For typical carcass joints made from chipboard or MDF, biscuit joints of this dimension are used almost exclusively.

Length x width: 56 x 23 mm
Thickness: 4 mm
Required cutting depth: 12,3 mm
Recommended board thickness: from 16 mm (ideal for the standard 19 mm dimension)

Usage and Choosing the Right Size

In practice, selecting the correct dimensions always depends on the board thickness of the workpiece. As a general technical rule: always choose the largest possible connector permitted by the material thickness and component width without the slot breaking through the edges.

When building a standard cabinet from 19 mm thick melamine-faced boards, size 20 biscuit joints are the technically correct choice. The cut is made precisely along the centre of the timber edge. If, on the other hand, you are joining narrow decorative mouldings, picture frames, or thin drawer fronts (e.g. 10 mm) with a mitre, size 0 must be used instead, as a deeper cut would break through the outer surface of the workpiece.

A significant advantage of this system is its tolerance for error along the longitudinal axis. Because the routed groove is always slightly longer than the connector itself, the components can still be shifted sideways by a few millimetres to align them completely flush before the glue cures.

Related Terms

Biscuit jointer: The specialist power tool that uses a circular blade (Ø 100 mm, thickness 4 mm) to cut precise slots into the wood before the biscuit joints are inserted.
Groove: An elongated recess or slot in a workpiece.
Wooden dowel: The cylindrical wooden predecessor that requires more precise drilling (usually 8 mm) and allows no lateral adjustment.
Cam and pin connector: A metallic fitting (often called a Minifix or cam lock) that joins carcass components in a demountable way, unlike a permanent glued joint.