Why are some Pokémon caught on the first try while others resist twenty Ultra Balls? It all comes down to a formula, which Black and White enrich with one novelty: Critical Capture. Here is what really matters, and how to choose the right Ball at the right time.

Each species has a catch rate, from 3 (the hardest) to 255 (the easiest). Audino is at 255, Darmanitan at 60, Volcarona at 15. All of Unova’s legendary Pokémon, from Kyurem to the Swords of Justice, are at 3.

To this rate are added three factors you control: the remaining HP, the Pokémon’s status and the Ball used.