What width should box joint fingers be?

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.

How strong are box joints compared to dovetails?

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.

Can I cut box joints on a table saw?

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.

WoodCalcs

Box Joint Calculator — Finger Joint Spacing

Calculate finger joint spacing and dimensions for strong, attractive box construction.

Board Width

Board Thickness

Desired Finger Width

Will be adjusted for even spacing

How We Calculate This

This calculator determines the number and size of fingers for a box joint.

The calculation

Number of fingers = Board width ÷ Desired finger width

The result is adjusted to an odd number so the joint interlocks correctly (one board has one more finger than the other).

Finger depth

Finger depth equals the mating board thickness, so the fingers sit flush when assembled.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.