Why are there different shoe sizes?

Confused on shoe sizing? You're not the only one.

Unfortunately there are a number of different systems in use.  The first problem is that the various international shoe sizes are based on different measuring systems.

• British shoe sizes are based on an imperial system with units of one-third of an inch.
• American shoe sizes for ladies are also based on an imperial system with units of one-third of an inch, however they use a different starting point to the British scale.
• European shoe sizes have a French metric origin with units based on two-thirds of a centimeter.

To further confuse the issue, a distinction in sizing is frequently made between Men's, Women's, Adult and Junior shoe sizes within the same scale, generally being a full size out across the range. For some illogical reason:

• a US Men's 5 is equivalent in size to a US Women's 6
• a US Men's 5 is approximately the same size as a US Junior 4
• a UK Adult 5 is approximately a UK Junior 4 (but of course both different from the equivalent US size!)
• a European Adult 35 is approximately a European Junior 34

To add a little more confusion, there are two scales used in the US, the "standard" (or "FIA") and "common" scales (apparently due to an error by the US Army during WW1).  Although the "standard" scale is more correct, the "common" scale is more widely used.  These are approximately ½ size different.

This is not to mention specialised systems such as Mondopoint for ski boots, skates and the like.

Many manufacturers over time have adopted their own sizing systems, that although they appear to conform with one system or the other, may be completely different.

Finally, some countries have their own measurement system. For instance, Korea appears to measure shoe size in millimetres leading to shoe sizes such as "225".