One's body shape also needs to be included in the formula; I'm a 44/46 chest, but my little keg o' Guinness whom I've acquired steadily over the last couple decades and resides just below there measures a bit shorter around, and then the remnants of my svelter youth, the waist/hips, chiming in somewhere in the mid-30s. I fit pretty snuggly into my XXL 5.0, with the collar standing just below the chin, and the bottom riding just around my belt. I tried on a bomber which due to softer fabric was more forgiving around the middle, neck and body length, and could probably accommodate some heavier clothing underneath, as well. As for the hoody, well, every man must know his limitations, and alas, for the sake of both decency and humanity, anything even remotely spandex-esque is one of mine...
The tricky part I think is the armor; whether your forearm fits by the shoulder pad, but not the elbow, or vice versa, etc. Unfortunately, it may require a try or two to get the right size jacket for you, but it'll be worth it. They're a great product.
Definitely give them a call/email; they were SUPER helpful with me when I was shopping for mine...