Pokémon Gen 4 Catch Rate Calculator

How Catch Rates Work in Generation 4

When you throw a Poké Ball, the game calculates a modified catch value (known as "a"). This value is determined by the Pokémon's innate Base Catch Rate, its missing health, the quality of the ball thrown, and any status conditions applied.

If the "a" value reaches 255 or higher, the catch is guaranteed. If it is lower, the game runs a complex square root equation to determine the chance of the ball shaking successfully. Our calculator simplifies this math into a straightforward percentage.

Poké Ball Modifiers and Multipliers

Not all Poké Balls are created equal. Knowing when to use specialty balls is the key to catching roaming legendaries like Entei or Raikou.

• Ultra Ball: Provides a flat 2x multiplier. Reliable, but expensive.
• Dusk Ball: Provides a massive 3.5x multiplier, but only if you are playing at night (between 20:00 and 03:59) or inside a cave/building. This is often the best ball in the game.
• Quick Ball: Provides a 4x multiplier, but only if thrown on the very first turn of battle.
• Timer Ball: The multiplier scales up every turn, reaching a maximum of 4x at turn 10 (30 turns in Gen 3 and 4, changed to 10 in Gen 5).

Status Condition Bonuses (Sleep vs. Paralysis)

Lowering HP is not always enough. To maximize your chances against a Catch Rate 3 legendary, you must inflict status conditions.

Poison, Burn, and Paralysis grant a flat 1.5x multiplier to the capture formula. Paralysis is highly recommended because it does not accidentally kill the target (unlike Poison or Burn).

Sleep and Freeze grant a massive 2.0x multiplier. Using Spore (from a Breloom or Parasect) to put a legendary to sleep will drastically cut down the number of balls you need to throw.

HP Percentage Impact

The less HP the wild Pokémon has, the easier it is to catch. The formula calculates the ratio of Current HP to Maximum HP.

To get the absolute best catch rate, you must lower the Pokémon to exactly 1 HP. The safest way to do this without accidentally knocking it out is by using the move False Swipe, which always leaves the target with at least 1 HP.