Just FYI Mondopoint is the most reliable system for shoe sizing. it is used by NATO and most armies nowadays and is now the ISO standard for shoe sizing.
Basically measure your foot in mm then round to the nearest 5mm and you will have your mondopoint size.
294mm foot? 29.5 mondopoint
277mm foot? 27.5 mondopoint. done
If mondopoint is there, use it, life made simpler.