Box Joint Calculator — Finger Joint Spacing

Finger width is largely aesthetic. Common choices are 6mm (1/4"), 10mm (3/8"), and 12mm (1/2"). Thinner fingers create more glue area and are stronger but harder to cut accurately. A good starting point is to match the finger width to the board thickness.

Box joints actually have more glue surface area than dovetails and can be stronger in tension. However, they lack the mechanical interlock that prevents dovetails from pulling apart. For boxes and drawers, both joints are more than adequate.

Yes, box joints are commonly cut using a table saw with a dado blade and a simple jig. The jig has a key that spaces each cut exactly one finger width apart. This is one of the easiest joints to cut accurately by machine.