Do this:
Forget about US and EU sizing numbers, they're too coarse a measurement and subject to being skewed by whatever they want to call a 11, 12, 13, etc. Most any legit shoe mfr will tell you the actual length measurement (in CM) of the shoe. Look online for a site that explains how to trace your foot but essentially you put your foot on a piece of paper a certain way and make an accurate tracing of it. Measure the length and you have your actual, universal, irrefutable foot size. Then look on whatever shoe chart you're eyeballing and choose the one that actually matches that value, not whatever arbitrary size they assign to it. You may even find that you have one foot larger than the other and have to buy a size up to accommodate.
I've had so much better luck shoe shopping like this and have also bought a new pair of the new 2FO canvas flat shoes without having tried them on and they fit spot on. Most shoes i fall into a 48/49 or whatever but can never tell since i cant try them on anywhere. Buying based on CM makes it easy. If you're a 'tweener, buy both and send the ones that don't fit back.