With new regulations in China taking in effect recently, online games containing crates and loot boxes now have to reveal the probability each item has. Now we have exact chances of what item you can get in the game Overwatch.
Through the official Blizzard website, the site has revealed that that every loot box always contains at least one Rare (blue) item. On average, players receive an Epic (purple) item every 5.5 loot boxes and a Legendary (orange) item every 13.5 loot boxes
The numbers apply for the Chinese version of the game of course, but these numbers most likely apply to every version of the game. Overwatch is available to purchase on PC, PS4, and Xbox One