What is the difference between a cake board and a drum?

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.

How much bigger should the drum be than the cake?

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.

What thickness drum do I need?

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.

Do I need boards between each tier?

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.

BakeCalcs

Cake Board & Drum Sizing Calculator

Calculate the correct board and drum sizes for tiered cakes.

Number of Tiers

Cake TypeRound and square boards are both sized as tier dimension plus overhang (enter the diameter, or the side length for square). This sets how your result is labelled — square drums still need corner clearance for boxing and transport.

Display StyleAll on one drum: one rigid base drum with thin hidden cards (sized to each tier) between stacked tiers. Individual boards: every tier on its own visible board or drum with a decorative overhang. Combination: a drum under the base tier plus hidden same-size cards for the tiers above.

Tier Diameters

Tier 1 (bottom)

Tier 2

Tier 3 (top)

How We Calculate This

The calculator determines the correct board and drum sizes from your tier diameters and preferred display style. Board and drum sizing is linear — it adds an overhang to each side of the dimension you enter (this is not the same as scaling cake batter, which grows with the area of the tin). A visible base drum gets a decorative border, while cards that sit hidden between stacked tiers are cut to match the tier they support.

The Calculation

Base drum = Bottom tier dimension + (base overhang × 2). The default 2.5cm per side gives the standard UK 5cm / 2-inch larger total diameter.
Stacked cards (all-on-one-drum and combination styles) = same size as the tier above, so they stay hidden once assembled.
Individual display boards = Tier dimension + (board overhang × 2), as each is visible.
Drum thickness based on the total number of tiers — 12mm for cakes up to 3 tiers, 15mm (or doubled 12mm) for 4-5 tiers.

Frequently Asked Questions

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Last updated: March 2026

All calculations are based on standard ratios and conversions. Results may vary with specific ingredients, equipment, and conditions.