Pokémon Catch Rate Calculator
Estimate your chance of catching a wild Pokémon with a single throw — from its catch rate, HP, ball, and status.
Four things matter
Species catch rate, how low the target's HP is, which ball you throw, and any status condition.
HP and status do the heavy lifting
Dropping a Pokémon to red HP and putting it to sleep can swing the odds more than a better ball.
What is a catch rate?
Why some Pokémon resist the ball
Every Pokémon species has a fixed catch rate — a number from 3 to 255 stored in the game data. A higher number means an easier catch: early-route Pokémon often sit at 255, while legendaries are pinned at 3. As community references such as Bulbapedia and Pokémon Database document, the game does not roll directly on that number. It first builds a modified catch rate from your situation, then runs four "shake" checks that decide whether the ball holds.
This calculator uses the Generation III/IV formula, the version most catch-rate guides quote. First the modified catch rate a is built, then it is turned into a probability.
a = (3·HPmax − 2·HPnow) / (3·HPmax) × catchRate × ballBonus × statusBonusThe HP term is the lever you control most: at full HP it equals one third, but as the target nears fainting it climbs toward one, tripling the effective catch rate. Once a is known, the game computes a shake value b = 1048560 / (16711680 / a)^0.25 and checks it four times; the catch succeeds only if all four checks pass, giving a probability of (b ÷ 65535)⁴. If a reaches 255 the catch is guaranteed, which is also what a Master Ball forces directly.
You are facing a wild Pokémon with a catch rate of 45 — say a mid-game Pokémon — and you want to know your odds with a plain Poké Ball at full HP.
Find the HP factor
At full HP the term (3·HPmax − 2·HPnow) ÷ (3·HPmax) equals 1 ÷ 3 ≈ 0.333.Build the modified rate
a = 0.333 × 45 × 1 (ball) × 1 (no status) ≈ 15.Convert to a probability
With a = 15 the four-shake formula gives roughly 5.9 % per throw.Improve the odds
Drop the target to about 25 % HP and put it to sleep and the same Poké Ball climbs to nearly 30 % per throw.
Players often over-invest in fancy balls and under-use the two free levers — HP and status.
A better ball helps a little
An Ultra Ball only doubles the rate; against a stubborn target that may still leave you well under 20 %.
Low HP helps a lot
Red-zone HP nearly triples the effective rate versus a full-HP target.
Status stacks on top
Sleep or freeze doubles again, multiplying with the HP and ball bonuses.
This is why the standard advice from competitive and collection communities like Smogon and Serebii is the same: weaken, status, then throw. The ball is the last and smallest multiplier.
The catch chance is the probability that a single throw succeeds under the
conditions you entered. The "average balls needed" is simply one divided by
that chance — a per-throw chance of 5 % means roughly twenty balls on average,
though luck means any individual attempt can be much faster or slower. The
modified catch rate a is the intermediate number the game builds before the
shake checks; when it reaches 255 the catch is certain. Because each throw is
independent, stacking a lower HP, a status condition, and a better ball
compounds your odds rather than just adding to them.
Knowing roughly where a species sits helps you decide how much to prepare before you start throwing balls. Catch rates cluster into recognisable tiers, and the right strategy follows from the tier.
Easy — 150 to 255
Early-route Pokémon and many common species. A weakened target catches reliably even in a plain Poké Ball, so you rarely need to stock up.
Moderate — 45 to 120
Mid-game Pokémon, evolutions, and pseudo-legendaries (catch rate 45). Plan on low HP plus a status condition and a Great or Ultra Ball, and expect several throws.
Brutal — 3 to 30
Legendaries and box mascots. Even at 1 HP and asleep, an Ultra Ball may only clear a single-digit-to-low-double-digit percentage — bring dozens of balls or save before the encounter.
Because a legendary's catch rate of 3 leaves almost no room to manoeuvre, the only levers that meaningfully help are dropping it to a sliver of HP, keeping it asleep or frozen, and throwing your best non-Master ball repeatedly. This calculator lets you check the exact odds for any combination before you commit, so you can judge whether to throw now, weaken further, or reset the encounter entirely.
This is a model of the core mechanic, not a guarantee for every game.
Generations and special balls differ
The exact constants changed across generations: later games nudged the sleep/freeze bonus to ×2.5 and added situational balls (Dusk, Net, Quick, Timer) whose multipliers depend on time, terrain, or turn count. This calculator uses the widely cited Generation III/IV values with the universal balls, so treat the number as a close estimate rather than a frame-perfect figure for a specific title. Always confirm a species' catch rate against a current source before a critical throw.