How do cross-halving joints work for dividers?

Each divider has slots cut halfway through its height. One set of dividers has slots from the top, the other from the bottom. They interlock at each intersection, creating a rigid grid without glue.

How thick should box dividers be?

For small decorative boxes, 2-3mm plywood or veneer works well. For tool boxes, 4-6mm plywood is stronger. The divider thickness reduces compartment size, so thinner is generally better for small boxes.

How do I cut accurate divider slots?

Use a table saw or router with a straight bit matching the divider thickness. Stack dividers and cut all matching slots at once. A dado blade on a table saw makes quick work of multiple slots.

WoodCalcs.uk

Divider Calculator — Box Compartment Dividers

Calculate divider dimensions and slot positions for compartmented boxes with cross-halving joints.

Internal Length

Longest dimension of the area

Internal Width

Shortest dimension of the area

Internal Height

Internal depth of the box from the base to the rim

Columns (along length)

Number of compartments along the length — creates Columns − 1 cross dividers

Rows (along width)

Number of compartments along the width — creates Rows − 1 long dividers

Divider Thickness

Material thickness

How We Calculate This

This calculator determines divider dimensions and cross-halving slot positions for a compartmented box.

Compartment size

Compartment length = (Internal length - divider space) / number of columns

The divider space accounts for the combined thickness of all dividers running in that direction.

Cross-halving slots

Each intersection requires two slots (one from top, one from bottom), each cut to half the divider height.

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.