Every company tends to have a different style of measurement. I'd say in terms of true sizing, Nike is your best bet/most accurate. Within their line of shoes, sizing is pretty consistent. read more
The same cannot necessarily be said about adidas' line -- the Ultra Boost run very small, while the Tubulars/Tubular Doom/Yeezy's run quite large. When you're assessing the size of a shoe, there are two primary factors: length and width. read more