How to use it
Choose centimetres or inches. For each tier, pick round or square and put in the size across: the diameter of a round tier, the side of a square one. Leave a size empty to skip that tier. Then choose finger or dessert portions, or type your own, and put in how many guests the cake needs to feed.
How it is worked out
The method is ours. A portion is a small rectangle seen from above, the full depth of the tier. Our starting sizes are 2.5 by 2.5 cm for a finger portion and 2.5 by 5 cm for a dessert portion. They are not a standard, so change them to match your baker's.
A square tier is cut in a grid, so it gives whole rows times whole columns: a 20 cm square gives 8 by 8, which is 64 finger portions. A round tier is worked out by its area, pi times the radius squared, divided by one portion, and rounded down. A 20 cm round tier gives 50 finger portions. Cutting a round cake into a grid loses a little at the curved edge, so the real count can be a few fewer.
Inches are turned into centimetres at exactly 2.54 cm to the inch.
Still planning? Try the drinks calculator and the planning checklist.