when you're measuring like that, you're actually falling onto the Mondo size scale. There are equivalencies to the other size scales, US, UK & Euro. Each manufacturer will have a slightly different length/fit. I suggest getting a self-sizing chart, for the shoe manufacturer you plan on buying from - IE - SIDI does have such as paper scale you can download, print out and measure from. Their's is accurate for their shoes. I would expect most of the better known shoe manus will also have their own similar paper scale.