.. yet we do not have a single standard sizing system, in fact there are three base systems and now many sub-systems and interpretations of these, this page will look at the rules for these systems, please do not use any information here as the basis for buying shoes though as the manufacturers have applied their own twist which is covered separately.
As mentioned, regarding foot length there are three primary systems in use globally with each having it's derivatives, this makes for sufficient complexities to warrant an explanation however there are multiple other "gotcha's" to consider too, as we'll see only a rudimentary comparison across systems is possible. Let's start with these official systems then review against what is actually happening...
This applies to the UK, USA, Australia, Canada, New Zealand, Ireland.
Children's and junior sizes: The sizes begin at 0 and incrementing till size 13 at which point the adults sizes begin. Size 0 is located at 4 inches (the size of a 'hand') and each size increments as the length is increased one third of an inch (1/3rd inch is another old measurement unit - the 'barleycorn') right up to size 13.
In the US and Canada the Junior scale starts at 3 and 11/12ths of an inch. Contrary to popular belief it does start at zero.
Note: both male and female shoe sizes are identical in child sizes.
also I've included four pink tape measures, the need for these is due to the fact that these systems are based on last measurements (the 'last' is a foot shaped block to form the shoe on during construction) so the first two tape measures are the dimensions of the last. Of course we're interested in actual foot size this is where the second pair of pink measures come into effect - for child sizes its advisable to add around 12mm (half an inch) to the actual foot length.
Adult sizes: These continue on from the junior sizes with adult size 1 being one barleycorn (one third of an inch / 8.47mm) greater than size Jnr 13. That's as far as simplicity goes though, from now we start to see a greater degree of variance.
Note the 'wriggle room' has increased from 12mm to 17mm.
As you can see Australia (and New Zealand) operate a separate system for female adults shoe sizes, this ranges between British plus one size through British plus two and a half and also in some cases being pegged to the US. Additionally in the US and Canada the female adult sizes are presented on a different scale (in fact two different scales) firstly "the common scale" typically 1.5 sizes up from the male scale and secondly "the standard scale" which has female sizes at male plus one. There are some references to the common scale being more popular however my initial investigations haven't borne this out.
This applies to most of continental Europe. Germany, France, Italy, Spain, Sweden, Poland and more. In Latin America too Brazil has adopted a version of it.
Paris Point is a straightforward system for measuring shoe size length. Quite simply it's a scale that starts with a size zero and increments every 2/3rd's of a centimetre (6.67mm). The system is used for children, adults and is genderless.
Childrens and junior sizes:
As with the British based systems the measurements are based on the size of the 'last' indicated by the first two pink rulers, this means that consideration is needed for 'wriggle room' a rough guide is 12mm for children and juniors.
Adults both male and female:
The chart shows the 'wriggle room' increasing to 17mm for adults jump to fitment.
This applies to most of Asia, countries actively adopting it are Japan and Korea.
The metric system is almost certainly the future of shoe measurement, having studied the other systems it can't happen soon enough. The name that you'll hear more and more often is Mondopoint (literally "Worldpoint") currently in use for ski boots and military footwear - I hope it spreads.
Childrens and junior sizes::
(12mm for toe wriggle room)
Adults both male and female:
(17mm used for adults wiggle room)
Japanese sizes: are measured in centimetres and indicate the actual size of foot that will fit. When finding your own size round up to the next half a centimetre.
Chineses sizes: since 1998 China has been adopting the Mondopoint system, although you will find traces of historical lengths it's far better to use mm.
Korean sizes: also uses mm.
So now we've established the core systems and how they relate to foot length let's show them side by side. When using this chart though please remember that manufacturers will vary in their adherence to this scale. For example many simply add 1 or 0.5 to a British size to generate a US size, in Europe there can be a whole size difference between France and Italy. If the manufacturer has a scale against intended foot length (some do but not many) then use theirs instead.
So there we are, very colourful and utterly useless as a size guide... but this knowledge helps us understand the history behind where we are at today. These few systems can be interpreted in many ways giving rise to many misunderstandings we see on hundreds of websites (some which would normally be authoritative in many subjects) all spouting different answers, the underlying cause is of course a lack of an adopted standard between manufacturers. There is growing adoption of the Mondopoint system which takes foot length/width) and not last length/width into consideration, so in theory once you're aware of your foot size then you can happily buy that size from any manufacturer knowing they should fit. Only one problem with Mondopoint is that although it's a step forward [sic] it's still only two dimensional and our feet have of course four. Until technology provides a way of scanning our feet change shape under load in the average shoe shop then Mondopoint's adoption should be encouraged.
I'm still collating manufacturer sizes for comparison, feel free to visit my google plus page for progress updates and/or offer feedback.
Additional reading.Case study on shoe length fit for people with diabetes. Wordy but fascinating read for diabetics and general footwear choice.
If you have written or would like to submit other non-commercial works for inclusion here then please get in touch.
Measure your feet! It may be that you've not have your feet measured for years or are even relying on a measurement from that day you discovered those killer shoes and had to go up a size for a suitable width. Whatever the story get them measured - it's simple and quite empowering. A couple of points though - measure whilst standing up (half a barleycorn difference in some instances), measure both feet and use the longest. If you're unable to do this then head for the shops but make sure you understand and note down what system they use, the Brannock system is popular in stores but it's aligned with the US standard size - ideally request the mm actual foot size.