Pokemon Catch Rate Calculator

Gotta Catch 'Em All: Understanding the Math Behind the Capture

Every Pokemon trainer has experienced the frustration: A Legendary Pokemon is down to 1 HP, asleep, and you've thrown thirty Ultra Balls, but it immediately breaks out. Why? The answer lies in the Catch Rate Formula, a complex algorithm that runs every time a ball hits a Pokemon. This guide explores the variables that determine whether you catch your target or waste another turn.

The Core Variables

While the exact formula has shifted slightly between generations (e.g., from Gen 1 to Gen 9), the core principles remain consistent:

1. Max HP vs. Current HP

The health bar is the most critical factor under your control. The formula essentially compares the percentage of missing health to the total health.
Rule of Thumb: A Pokemon at 100% HP is significantly harder to catch than one at 1% HP. In the standard formula, reducing a Pokemon to 1 HP roughly triples your catch chance compared to full health.

2. Catch Rate (Species Rate)

Every Pokemon species has a base "Catch Rate," an integer between 0 and 255.
255 (33.3% Base): Very easy. Pidgey, Rattata, Caterpie. A full-health Poke Ball often catches them.
45 (5.9% Base): Medium difficulty. Starters, evolved forms, Onix.
3 (0.4% Base): Hardest. Legendaries (Mewtwo, Rayquaza), Beldum. Even at 1 HP and asleep, these are tough.

3. Ball Bonus

Your choice of equipment matters massively:
Poke Ball: x1.0 multiplier.
Great Ball: x1.5 multiplier.
Ultra Ball: x2.0 multiplier.
Dusk Ball: x3.0 multiplier (at night/in caves). This is strictly better than an Ultra Ball in the right conditions.
Quick Ball: x5.0 multiplier (First turn only). The single best ball for casual catching.
Master Ball: Skips the formula entirely. 100% success.

4. Status Conditions

Inflicting a status ailment is the pro strat:
Sleep / Freeze: Provides a massive ~2.5x multiplier. Sleep is generally safer than Freeze (which is rare to inflict reliably). Spore and Hypnosis are your best friends.
Paralysis / Poison / Burn: Provides a ~1.5x multiplier. Paralysis (Thunder Wave) is popular because it doesn't wear off like Sleep and doesn't kill the Pokemon like Poison/Burn.

The "Shake Checks"

When the ball wiggles, the game isn't just playing an animation; it's running a math check. In modern games, there are usually four "shake checks."
The game calculates a "modified catch rate" (called a) and then checks if a random number is less than a certain threshold derived from a. If the check passes 4 times, the Pokemon is caught. If it fails on the 1st check, the ball breaks immediately. If it fails on the 3rd, it shakes three times then breaks, causing maximum emotional damage.

The Critical Capture

Introduced in Gen 5, a "Critical Capture" occurs when the ball makes a distinct whistling sound and only shakes once. This rare event greatly increases capture probability and is influenced by how many Pokemon you have already caught in your Pokedex (an achievement bonus).

Strategy for Legendaries

1. Turn 1: Throw a Quick Ball. (4-5x chance).
2. Weakening: Use "False Swipe" to bring HP to exactly 1. False Swipe always leaves at least 1 HP.
3. Status: Use Spore or Sleep Powder to induce Sleep.
4. The Throw: Use Dusk Balls (if in a cave/night) or Ultra Balls. Reset the Sleep status immediately when they wake up.
5. Patience: Even with perfect conditions (1 HP, Sleep, Ultra Ball), a Legendary like Mewtwo might only have a ~6-8% catch chance per ball.