"Keep in mind that shoes sizes are somewhat arbitrary between manufacturers".
I recently had the experience of being measured for my shoe size with the Brannock scale during a dress shoe purchase and while it indicated one size it differed wildly from what I actually wear in my hiking shoes.
For example I have a pair of dress shoes that I have worn for many years. They are lace ups that are comfortable and I am able to slip them off without untying the laces. These shoes are a size 9.5 US.
The Brannock scale said that I should wear a size 10. The new dress shoes that I wound up purchasing turned out to be a size 10.5. On the surface this sounds like everything agrees with what was said in the posts above except for the older pair of size 9.5 shoes.
Here is the rub. I hike in Merrell Moab Ventilators size 11.5 and still find the front of the shoe on some downhill sections of trail. I may soon upsize to the size 12 Merrells.
Try them on before you buy them. The numbered sizes should follow the Brannock scale but they don't always. As far as the width of shoes goes, I have found some D widths confining in shoes made by some manufacturers. But when I tried on the "wide" version of my Merrells it was laughable how much side to side room there was in there.
Try them on before you buy them and if you even think for a moment that you might need just a little extra length, Do It!
Hammer toe ain't pretty and it doesn't feel good at all.
Party On,
Newton