Cake Sizes in Kilograms: Why We Quote Inches Instead

Because in a great deal of the world that is simply how cake is bought. In India, across the Middle East and in much of Eastern Europe a cake is ordered by weight — half a kilo, one kilo, two kilos — and the bakery scales the recipe to the number. British and American bakeries grew up quoting the tin instead: a round cake is a diameter in inches, and the portions follow from it.

Neither habit is wrong, and if you grew up with kilograms then asking for inches feels like being asked for your height in hands. The trouble is that the two do not convert cleanly, and a bakery that gives you a tidy conversion is guessing. The table below is what this kitchen quotes from instead.

It depends entirely on what the kilogram is made of, which is the whole problem with the question. A light sponge of a given diameter and a layered honey cake of the same diameter are nothing like the same weight: thin layers soaked in cream are dense, and an airy sponge is mostly trapped air. Two cakes that look identical on the table can differ in weight by half again.

So weight runs in the wrong direction as a serving measure. The thing a guest eats is a slice — a wedge of a certain width taken from a cake of a certain height — and that is set by the diameter and how the cake is cut, not by what it weighs. A heavy cake cut thinly feeds more people than a light cake cut generously, and the scales know nothing about either.

Two numbers, and they are the ones every quote here starts from: how many people are eating, and whether cake is dessert or something handed round. From those a size follows directly, and the price with it. If you have been given a weight by somebody else and want to compare, ask them the same question — how many portions, cut how — and compare portions against portions.

Three things are worth saying plainly when you ask. Who is eating, because children take a child's slice and a room of adults after a meal takes a sliver. Whether anybody is serving, because a cut cake handed round goes much further than a plated dessert. And the occasion, because a cake that has to be the centrepiece is bought for its height as much as its portions.

Yes, and that is the one place where thinking in quantities rather than in sizes genuinely helps. The price of a cake is mostly hours and only partly ingredients, and the hours do not double when the diameter does — covering a larger cake takes a little longer than covering a small one rather than twice as long. Divide each price in the table above by its portions and the cost per slice falls as the cake grows.

The practical consequence is the opposite of buying by weight. If you are between two sizes, the larger one is better value per person as well as safer, and the leftover slices cost you nothing because they go home with your guests. Buying two small cakes to feed one room is the most expensive way to arrive at the same number of portions.

Not as a quoted product, and the reason is honesty rather than awkwardness. A cake made to hit a number on the scales would have to be weighed finished, cream and decoration included, and the decoration is the part that varies most — a crown, a board of berries or a sugar plaque all weigh something and none of them is cake. A quote against a weight would be a number nobody could check without destroying it.

What can be done is the thing underneath the request. Tell us the number of people you were going to express as a weight, and the answer comes back as a diameter, a portion range and a price, with the lead time of 7–10 days, or at least 14 for two tiers and delivery from £30 if you need it. That is the same information in the units this kitchen can stand behind.