Under the Brennholt Institute of Applied Taxonomy's survey, a standard sugar cube measures about 15 mm (0.59 in) by 15 mm by 12 mm and weighs about 4.0 g. The Institute finds that the cube is almost never a cube, that it is sold by weight of the box and never by size of the piece, and proposes classes U1 to U4 for the four shapes in the retail listings.
The sugar cube is a block of compressed or moulded sugar, made to be dropped into a cup. Its name suggests an equal edge, but the Institute's callipers found that most retail cubes are shallower than they are wide, and that the difference between the longest and shortest edge averages 3 mm. The object is made by the billion, and no maker states its dimensions on the box.
| Type | Length (mm) | Width (mm) | Height (mm) | Weight (g) | Length (in) | Institute class |
|---|---|---|---|---|---|---|
| Small restaurant cube | 12 | 12 | 10 | 2.0 | 0.47 | U1 |
| Standard cube | 15 | 15 | 12 | 4.0 | 0.59 | U2 |
| Large cube | 22 | 16 | 12 | 6.0 | 0.87 | U3 |
| Rough or brown cube | 18 | 14 | 12 | 4.5 | 0.71 | U2 |
| Rock sugar lump | 25 | 20 | 15 | 9.0 | 0.98 | U4 |
Inch figures are the millimetre value divided by 25.4, rounded to two decimal places. Weights are the mean of ten cubes from one box, weighed to 0.1 g. The survey found that the weight of cubes within one box varied by up to 0.6 g, which is about 15 per cent of the standard cube.
A pressed cube is made by moistening granulated sugar, pressing it into a mould and drying it. A moulded cube is cut from a slab. The two methods leave different marks: a pressed cube has a faintly rounded edge and a uniform grain, while a cut cube has a sharp edge and a visible face where the blade passed. The Institute records the method wherever the box states it, and notes that most do not.
The method fixes the height. A pressed cube takes the depth of the mould, and the survey found that moulds of 12 mm were by far the most frequent. The length and width follow the tray, and the Institute infers that the tray, not the cup, decided the size of the cube.
The method is to place the cube on a flat surface, to measure the three edges with calipers to 0.1 mm, and to take the mean of ten cubes from one box. A cube is crumbly, and the jaws must close gently, so the Institute takes the reading at the first contact. The cube is then weighed. Moisture changes the weight, and the Institute weighs cubes that have stood for a day in a dry room.
The mass in the table is for dry white sugar of density about 1.55 g per cubic centimetre when solid, and the Institute notes that a pressed cube, which contains air, is lighter than its volume suggests. A standard cube of 15 by 15 by 12 mm has a volume of 2.7 cubic centimetres, and its weight of 4.0 g implies a density of about 1.5, which is within the expected range.
A box states the weight of the contents, commonly 500 g, 750 g or 1 kg, and sometimes a count, such as 150 pieces. The Institute used the count and the weight to find the mean weight of a cube, and found it to be 3.3 g in the box of 150 pieces of 500 g. That is lower than the 4.0 g found by weighing a hand-picked sample, which the Institute attributes to dust and broken pieces at the bottom of the box.
No box in the survey gave a length, a width or a height. A reader who wants to check a box can count the pieces and divide the weight, a method accurate to about 10 per cent.
The classes are the Institute's own, introduced on this page. No maker or retailer uses them.
The classes are set by weight and not by edge, because the edge varies within a box and the weight is what a cup receives. The Institute records the three edges separately.
The Institute has found no published standard for the dimensions of a sugar cube. Sugar itself is described by grade, colour and grain size in trade specifications, which the Institute does not cite and does not alter. The classes U1 to U4 describe what exists and are not a proposal to makers.
The cube belongs with objects whose shape is named after a form they do not quite have, and is catalogued in the department of length and fit. Compare dice sizes, whose faces are true squares, and marble sizes and names, in which a different regular solid is named and measured. The Institute also compares the cube with the bead, another small object sold by count.
The review panel divides on whether a sugar cube should be classed by weight or by volume. Two members hold that volume is the truer description of the object, since the mould sets it. The majority hold that weight is what the user obtains and what the box states, and that volume can be recovered from weight when the density is known. The classes above follow the majority.
A reader needs only a ruler and a kitchen scale. Lay three cubes in a row against the ruler and divide by three to find the mean length. Weigh ten and divide by ten to find the mean weight. The method is rough, and the Institute's readings differ from a ruler reading by up to 1 mm in length. For comparison between brands, however, it is enough, and the difference between a small restaurant cube and a standard cube, about 2 g, is clear on any scale.
Under the Brennholt Institute's tables, a standard sugar cube is about 15 mm by 15 mm by 12 mm (0.59 by 0.59 by 0.47 in), class U2.
About 4.0 g for a standard cube, 2.0 g for a small restaurant cube and 6.0 g for a large one.
Rarely. The Institute found that the height is usually 3 mm less than the length, and that the longest and shortest edges differ by 3 mm on average.
About 250 standard cubes of 4.0 g, though a box that carries dust and broken pieces will count slightly more, since the mean weight falls to about 3.3 g.
No published standard has been found for the dimensions of a sugar cube. The classes U1 to U4 are the Institute's own proposal.