How many slices does a 24 cm cake make?

A 24 cm round cake makes about 12–16 normal-sized slices. With smaller coffee-table pieces, up to 20. The calculator works out the exact number based on the slice size.

What size cake for 20 people?

A roughly 26–28 cm round layer cake is enough for 20 people with normal slices. The calculator works out the exact size based on the number of guests and the portion size.

Round or square cake?

A square cake yields slightly more even-sized slices and is easier to cut. A round cake is a more traditional party cake. The surface area determines the number of servings.

How much cake per person?

At a coffee table a small piece is enough (~20 cm²), as a dessert a larger one (~40 cm²). If several cakes are on offer, plan for less of each.

Cake Size Calculator — Servings

Calculate how many servings a cake yields or what size cake you need for a party. Free cake size calculator.

Number of guests: 12 people

Slice size: Normal

21 cm

Recommended cake diameter

Required surface area	360 cm²
Round cake, diameter	21 cm
Square cake, side	19 cm
Slices from a 24 cm cake	15 slices

ℹ️ The estimate is based on a slice of about 30 cm² for a normal portion. A tall layer cake serves more people than a low one. Reserve a little extra in case some guests want a second slice.

This cake size calculator helps you choose the right cake for a party or work out how many people a finished cake will serve. It supports both round and square cakes, so planning is easy.

How the calculator works and what it’s for▾

How the size is calculated

The calculator starts from the number of guests and the slice size, then converts them into the surface area you need. From that it derives a suitable diameter for a round cake and a side length for a square one.

The estimate is based on a slice of about 30 cm² for a normal serving, which matches a typical party portion.

What you enter and what you get

Enter the number of guests and choose the slice size. The calculator shows the required surface area, the diameter of a round cake, the side of a square cake and how many slices you get from a standard 24 cm cake.

This lets you see at a glance whether your planned cake is enough or whether you should go a size up.

Height affects how far it goes

A tall layer cake serves more people than a low cake of the same diameter, because the slices can be cut thinner. Keep this in mind if you make a rich, multi-layer cake.

Chocolate and heavily filled cakes are often served in smaller slices than light sponge cakes.

Party tips

Allow a little extra in case some guests want a second slice or unexpected visitors arrive. Any leftover cake keeps well in the fridge for the next day.

🔄 Reviewed June 2026