A Pokémon’s Capture Rate depends on its Level, Hit Points, Status Afflictions, Evolutionary Stage, and Rarity.

Normally, a Pokémon’s Capture Rate starts at 20, but in the event you want the Pokémon to be more difficult to catch, like if it were a Boss, Shiny, or a Legendary Pokémon, then raise this number by a value between 5 and 20 based on what you feel is appropriate for its rarity.  Remember that Pokémon that have been Knocked Out cannot be captured; Poké Balls will simply fail to attempt to energize them.

Next, follow the following checklist and adjust as needed.
* Is the Pokémon under level 25?  If so subtract 4 from its Capture Rating.
* Is the Pokémon's HP at or under 50% its max HP?  If so subtract 2 from its Capture Rating.
* Is the Pokémon's HP at or under 25% its max HP?  If so subtract another 2 from its Capture Rating.
* Is the Pokémon suffering from 5 or more Injuries?  If so, subtract 4 from its Capture Rating.
* Is the Pokémon suffering from a Persistent or Volatile Status Condition?  If so, subtract 2 from its Capture Rating (These do not stack for each condition!)
* Does the Pokémon have two evolution stages remaining?  If so, subtract 4 from its Capture Rating.
* Does the Pokémon have one evolution stage remaining?  If so, subtract 2 from its Capture Rating.

The Capture Roll is 1d20, with a bonus for Trainer tiers (+1 for Level 5, +2 for Level 10, etc)