Cake Board & Drum Sizing Calculator

A cake board (or card) is typically 2-3mm thick and sits between tiers or under lighter cakes. A cake drum is 12-15mm thick and provides a sturdy, rigid base for the bottom tier or the entire cake. Drums are essential for heavy or tiered cakes to prevent sagging or breakage during transport.

The standard UK recommendation is a drum about 5cm (2 inches) larger in total diameter than the bottom tier — roughly a 2.5cm (1 inch) border all the way around. So a 25cm bottom tier sits on a 30cm drum. This gives enough room for decoration and a neat finished look. For heavily decorated or wedding cakes, go 7-10cm larger in total diameter (3-4 inches). The Advanced Options default of 2.5cm overhang per side produces exactly this 2-inch total increase.

A 12mm drum is suitable for most cakes up to 3 tiers. For 4-5 tier cakes or very heavy cakes, use a 15mm drum or double up two 12mm drums. The drum must be rigid enough to support the total weight without flexing when lifted.

Yes, always place a thin cake card between each stacked tier. The card sits on top of the lower tier and the upper tier sits on the card, distributing weight across the dowels below and making the tiers easy to separate for serving. Cut the card to the same size as the tier it supports so it stays hidden once the cake is assembled. That is why this calculator sizes the stacked cards (in the "all on one drum" and "combination" styles) to match each tier exactly, while only the visible base drum and individual display boards get an overhang.