Cake Serving Calculator
Enter the shape, size and number of layers to see how many portions the cake will give.
A taller cake means each slice can be cut narrower.
Answer
About 15 party portions, or 10 dessert portions
Common tin sizes
- Party portions are the small fingers of cake handed round at a birthday or wedding. Dessert portions are the wedges you would sit down to with a fork.
- Rich fruit cake and heavy chocolate cake go further than a light sponge, so lean towards the smaller number.
- These are approximate. How a cake is cut makes as much difference as how big it is.
Source: Standard UK catering and home-cooking portion guidance · Reviewed 2026-09-10 · Guidance version 1.0.0
Reference and detail
Party portions and dessert portions
A party portion is the small finger of cake handed round at a birthday or wedding: about 2.5cm by 5cm. A dessert portion is the wedge you sit down to with a fork, roughly half again as big. The same 20cm cake gives about 24 of the first or 16 of the second, which is why serving numbers vary so wildly between sources.
Square cuts more than round
A 20cm square tin holds about 27% more cake than a 20cm round one, and it cuts into neat rectangles with no awkward offcuts. If you need to feed a specific number, square is the easier shape to plan.
Rich cake goes further
Fruit cake, dense chocolate cake and anything heavily iced is cut smaller than a light sponge, so lean towards the lower number. And if the cake is the only pudding, budget a portion and a half a head, people come back.
Questions and answers
Questions about how many portions a cake gives
How many people does a 20cm cake serve?
It depends on how you cut it and how many layers it has. Enter your cake's size and shape above for both party and dessert portion counts.
A party portion is the small finger of cake handed round at a gathering; a dessert portion is the wedge you'd sit down to with a fork, and the two numbers can be very different for the same cake.
Does a square cake give more servings than a round one the same size?
Yes. A square tin holds more cake than a round tin of the same width, and it cuts into neat rectangles without the small offcuts a round cake leaves behind.
Do extra layers mean more servings?
A taller, multi-layer cake lets you cut each slice slightly narrower for the same generous look, so it gives a few more portions than a single layer of the same width. Enter the number of layers above to see the effect.
Should I count fewer servings for a rich fruit cake?
Yes. Rich fruit cake, dense chocolate cake and heavily iced cakes are traditionally cut smaller than a light sponge, so lean towards the lower of the two numbers the calculator gives you.
Guidance
Read the full guide
- Cake Tin Sizes and Recipe ScalingHow to bake a recipe in the tin you actually own: matching area rather than width, adjusting batter quantity, and what happens to the baking time.