Generally speaking, the US chest size in inches is equivalent to roughly 10 points less than the European jacket size. Example: a 56 Euro jacket will fit like a size 46/XL men’s US size. But this jacket runs a bit more snugly… I’d say about 1/2 sizes small as compared to most others. I’d estimate the US chest size to be about 11 points lower than the Euro size. I’d suggest you measure yourself with a tape and get your chest size and belly size, then use the size chart to pick the smallest size jacket that will be big enough for both your chest and belly using the chart below. Approximate US alpha sizes are also listed in the chart so you can check if the jacket size you choose is the same alpha size as you normally wear in men’s clothing.
I’d call the overall cut of this jacket “sport casual”. It is meant to fit snug, but it doesn’t taper nearly as much as sport/race jackets. The difference between the max chest and max belly is about 1”-2”.