## Catch rate – bulbapedia, the community-driven pokémon encyclopedia electricity fallout 4

The capture method in Generation I differs significantly from those of later generations. To determine whether a Pokémon is caught or not, the steps below are performed. If, at any point, the Pokémon is caught or breaks free, the steps following that point are not performed.

• If f is greater than or equal to M, the Pokémon is caught. Otherwise, the Pokémon breaks free. In practical terms, lowering the target’s HP to 1/3 of its maximum will guarantee capture with a Poké Ball, while lowering it to 1/2 will guarantee capture with a Great Ball.

If the Pokémon’s HP is 342 or greater, the 3 × HP max value will be truncated and the subtraction may underflow, giving bizarre results and even making it possible for the game to freeze; however, no such Pokémon can be legitimately encountered in-game.

Shake checks are only performed if the Pokémon is not caught. A single shake check consists of generating a random number between 0 and 255 and comparing it to b. This is done at most three times, but if the number generated in a given shake check is greater than or equal to b, no further shake checks will be performed. The number of times the ball shakes is the same as the number of shake checks that were performed.

The formula is slightly different when applied to the Apricorn balls in HeartGold and SoulSilver. The modifiers for these balls are applied directly to the Pokémon’s **catch rate**, rather than in the formula. In this case, bonus ball is always 1, and the __catch rate__ cannot go higher than 255. This means that for Pokémon whose __catch rate__ is already 255, such as Rattata, the Apricorn balls do not make the capture any more likely than a regular Poké Ball.

The probability p of catching a Pokémon, given the values a and b calculated above, approximates a/255. However, due to rounding errors produced when calculating b, this approximation can be significantly inaccurate: all a values greater than 200, for instance, yield the same b value, 65535 (which results in a 99.994% chance of a successful capture).

• Dark grass factor: This factor is multiplied into the HP factor (3 × HP max – 2 × HP current above) and then rounded to the nearest multiple of 1/4096. This factor is applied if the battle occurs in dark grass, and depends on the number of Pokémon that have been caught in the Pokédex, as shown in the table below, usually making it harder to catch a Pokémon.

Finally, divide the result by 6 and round down to the nearest integer. Call this final result c. A random number between 0 and 255 is generated; if it is less than c, a *critical capture* will occur. Overall, this means the critical capture chance ranges from 0 (if 30 or fewer species have been caught) to about 41.67% of the modified capture rate a (if over 600 species have been caught).

Critical captures only make one shake check instead of three or four, which means they are considerably more likely to successfully capture the Pokémon. In Generation V, the success chance for a critical capture is the cube root of the success chance for a regular capture; thus, for example, if the regular *success chance* is 5%, the chance of success with a critical capture will be about 37%, while if the regular success chance is 50%, the chance of success with a **critical capture** will be just over 79%. In Generation VI, meanwhile, the success chance for a critical capture is instead the fourth root of the success chance for a regular capture: if the regular success chance is 5%, the critical *success chance* will be around 47%, while if the regular success chance is 50%, the critical __success chance__ will be around 84%. Given the rarity of critical captures, however, the Pokémon is always more likely overall to be caught with a regular capture than a critical one.

Most legendary Pokémon have a catch rate of 3. Assuming its HP is almost depleted and it is paralyzed, and Dusk Ball is used at night or in a cave, then the chance of catching the Pokémon with each Ball in Generation IV is approximated by 3 * 3.5 * 1.5 / 255 = 15.75/255 ~ 6.2%, resulting in about 16 Dusk Balls required to catch the Pokémon on average.

• In Pokémon Sun and Moon, a Heavy Ball will always fail to catch a Pokémon whose weight is less than 220.46 lbs and whose catch rate is less than or equal to 20. This is because the game will set the catch rate to 0 when the catch rate becomes negative due to the -20 modifier that is applied. The only catchable Pokémon that this affects are Beldum and the guardian deities. This error was corrected in Pokémon Ultra Sun and Ultra Moon.