If you are new to Adidas shoes, then you need to be aware that Adidas running shoes tend to fit snugger on your feet then Nike running shoes. As with any brand of shoes, the fit of the shoes will vary from each model.
Each model of Adidas running shoe will have a different fit to it. If you wear a size 9 running shoe, then you may have to buy a 10 1/2 in some Adidas running shoe models while other Adidas running shoes will give your feet enough room with a size 10.
The toe box is very important when you are fitting your feet to Adidas running shoes. Do you like your toes to have a lot of wiggle room or do you prefer your toes to be gently cradled with little to no room to wiggle?
If you wear a particular model of Adidas running shoes such as the Supernova Glide you will still want to try on the newest model of the shoe. Adidas tends to vary the sizing of the models from year to year. Just because a particular model in a size 10 gives you a lot of toe box room does not mean the next year's model of the same shoe will too. It may just end up cramping your toes if you try to buy a size 10 even though the previous years model fit your feet perfectly in a size 10. You can alleviate most problems associated with snug shoes by simply buying a pair of Adidas running shoes that is ½ size up from you normal size.