Today (and since the 1960's) all drum toms dimensions are expressed in inches (imperial unit). Previously, many European brands (including ASBA) manufactured in metric dimensions. It was the arrival of synthetic drumheads from across the Atlantic (with Evans and Remo) that definitively imposed the international standard for drums now expressed in inches. Today, all drum manufacturers in the world have adopted this standard.
So to know the size of your drum, nothing could be simpler. It is the diameter that interests us, so you have to measure diagonally through the center of the drum with a tape measure. Yes, the tape measure is in fact expressed in inches, and it is the only easy tool to find in France to propose this unit. There are also the free paper tape measures offered by the Swedish furniture giant that have one side expressed in centimeters and the other in inches (keep the trick to yourself, eh?).
If you don't have any of that, we'll give you the formula to convert centimeters to inches here. Just measure the diameter of your barrel (in cm) and divide the result (counting millimeters) by 2.54. You get the dimension in inches.
To find out the depth of the drums, same struggle. You measure the drum from top to bottom, from edge to edge, then you divide the number of centimeters by 2.54. Simple as that!
To help you, we have made a little correspondence table ready to use:
8 inch shell = 20,32cm
10 inch shell = 25,4cm
12 inch shell = 30,48cm
13 inch shell = 33,02
14 inch shell (bass tom) = 35,56cm
16 inch shell (bass tom) = 40,64cm
18 inch bass drum = 45,72cm
20 inch bass drum = 50,08cm
22 inch bass drum = 55,88cm
24 inch bass drum = 60,96cm
26 inch bass drum = 66,04cm
The configuration of the kits in Europe is very often expressed in the following order: bass drum size; high tom size; medium tom size; bass tom size. Thus, a 20/10/12/14 kit means that the kit is composed of a 20 inch bass drum, a 10 inch high tom, a 12 inch medium tom and a 14 inch floor tom. Sometimes the size of the bass drum is placed at the end of the configuration, in ascending order: 10/12/14/20
In Europe, the size of a tom is expressed by its diameter X its depth. For example, a 10 inch tom with a depth of 8 inches will be translated as "10x8". But beware, in the USA, it is expressed in the other direction: 8x10!
The most common kit sizes are: 20/12/14; 20/10/12/14; 22/13/16; 22/10/12/16; 22/12/14/16