Under the Brennholt Institute of Applied Taxonomy's survey, paper cupcake cases are sold in five common base diameters, from 35 mm (1.38 in) to 60 mm (2.36 in), and the 50 mm (1.97 in) case is the most frequent in the retail listings. The Institute proposes classes K1 to K5 for these diameters, and records the wall height separately.
A cupcake case is a pleated cup of paper, foil or silicone that holds batter in a baking tin and is usually left on the finished cake. It is made in the billions and sold in packs of twelve to several hundred. The pack states a count and often a word such as mini, standard or jumbo. It almost never states a diameter in millimetres, and the words do not agree between makers.
| Common name | Base diameter (mm) | Base diameter (in) | Wall height (mm) | Batter volume (ml) | Institute class |
|---|---|---|---|---|---|
| Mini | 35 | 1.38 | 20 | 15 | K1 |
| Petite | 40 | 1.57 | 22 | 25 | K2 |
| Standard | 50 | 1.97 | 30 | 60 | K3 |
| Large | 55 | 2.17 | 35 | 90 | K4 |
| Jumbo | 60 | 2.36 | 40 | 120 | K5 |
Inch figures are the millimetre value divided by 25.4, rounded to two decimal places. The diameters are the Institute's survey means, measured across the flat base on a case lying empty and uncreased. The batter volumes are the quantity that fills the case to two thirds of its height, which is the usual working level, and they are indicative.
The Institute does not invent where a real rule exists. Baking tins are sold with cavities of recognised nominal sizes, and the muffin tin in particular is made in a standard cup and a mini cup by most makers. The Institute has found no published standard that ties the paper case to the tin. The case is made to fit the cavity by custom, and the Institute records that custom as a measurement, not as a rule.
The result is a loose fit. A case of class K3 sits in a cavity of about 70 mm across the top and 50 mm across the bottom, and the case is pleated so that it can stretch to the wall of the tin. A case that does not stretch, such as a stiff foil case, is chosen a size closer to the cavity.
The method is to lay the case on a flat surface, to read the diameter of the base from edge to edge across the centre, and to read the wall height from the table to the top of the rim at the pleat. A second reading is taken at the rim, where the case opens out. The rim is wider than the base by 15 mm to 22 mm, depending on the angle of the wall, and the Institute reports both figures so that a buyer can check the case against a tin.
Pleated cases are measured empty, and a case that has been squeezed in a pack is allowed to recover for an hour before measurement. A case that has held batter is not measured, since grease and steam change the paper by up to 2 mm.
The common case is of greaseproof paper, about 0.07 mm thick, and weighs between 0.3 g and 0.9 g depending on its class. A foil case of class K3 weighs about 0.8 g. A silicone case, which is reusable, weighs between 8 g and 15 g and holds its shape without a tin. The Institute records the material wherever the maker states it, since the material changes the effective size: paper shrinks slightly in the oven, and silicone does not.
Standing cases, which have a stiff wall and a flat base and need no tin, are measured on the same footing. Their base diameters follow the same five classes, but the wall height is greater, commonly 38 mm to 45 mm.
The classes are the Institute's own, introduced on this page. No maker or baking body uses them.
A class says how wide the base is. It does not say how much a case holds, since the height of the wall varies by maker. The Institute records the volume separately and does not infer it from the class.
Packs are sold in counts of 12, 24, 50, 100, 200 and 500. The Institute weighed a pack of one hundred K3 paper cases at about 55 g, including the sleeve. A reader can check a pack against a kitchen scale, with an allowance of 5 g. Colour and print carry no meaning of size, and printed cases are made on the same blanks as plain ones.
The survey of retail listings found that about one listing in four gave a diameter at all. When it did, the figure might be the base, the rim or the diameter of the tin cavity it was meant for, and the listing seldom said which. This is the main reason the Institute gives the base and the rim as two separate columns of work.
The cupcake case belongs with the tea bag and the sugar cube as a small kitchen article sold by count, and is catalogued in the department of length and fit. Compare tea bag sizes, which are also made of paper and also lack a published dimension, and sugar cube dimensions, which the Institute treats in the same manner.
The review panel divides on whether the base or the rim should define the class. Two members hold that the rim is what a baker sees and handles, and that classes should follow it. The majority hold that the base is the stable measurement, since the rim depends on how far the pleats are opened, and that the rim is a derived figure. The table gives the base, and the majority's position is the one used for the classes.
The Institute has not measured loaf cases or the deep cases used for large celebration cakes, which are made to order. Nor has it measured tulip cases, whose wall is shaped like a flower. Both are queued for a later survey, and no figure for them appears on this page.
Under the Brennholt Institute's tables, the standard cupcake case has a base of 50 mm (1.97 in) and a wall height of about 30 mm (1.18 in). It is class K3 and the most frequent case in the survey.
The Institute's mini case, class K1, has a base of 35 mm (1.38 in) and a wall height of about 20 mm (0.79 in). It holds about 15 ml of batter.
The Institute's working figure is about 60 ml for a class K3 case filled to two thirds of its height. The figure is indicative, since wall height varies by maker.
No published standard has been found that fixes the size of the paper case. It is made to suit the baking tin by custom. The classes K1 to K5 are the Institute's own proposal.
A paper case weighs between 0.3 g and 0.9 g in the Institute's survey, and a foil case of class K3 about 0.8 g. A reusable silicone case weighs between 8 g and 15 g.