Gen V Catch Rate Calculator B/W
Total health points of target
HP remaining (1 for False Swipe)
Base rate (3 to 255). Check Bulbapedia/Serebii.
Poké Ball (1x)
Great Ball (1.5x)
Ultra Ball (2x)
Master Ball (Always Catch)
Dusk Ball (Night/Cave) (3.5x)
Quick Ball (Turn 1) (5x)
Net Ball (Bug/Water) (3x)
Repeat Ball (Caught Before) (3x)
Timer Ball (10+ Turns) (4x)
Timer Ball (7-9 Turns) (3x)
Timer Ball (4-6 Turns) (2x)
Dive Ball (Underwater/Surfing) (3.5x)
Premier/Luxury/Heal (1x)
None
Sleep (SLP)
Freeze (FRZ)
Paralysis (PAR)
Poison (PSN)
Burn (BRN)
Gen V: Sleep/Freeze are 2.5x, others 1.5x
None
Capture Power ↑ (1.1x)
Capture Power ↑↑ (1.2x)
Capture Power ↑↑↑ (1.3x)
Capture Power MAX / S (2.0x)
Understanding the Gen V Catch Formula
Pokémon Black, White, Black 2, and White 2 (Generation V) introduced several changes to the capture mechanics found in previous games. Understanding how the game calculates success can significantly save your resources, especially when hunting legendaries like Reshiram, Zekrom, or Kyurem.
The core formula determines a "Modified Catch Rate" ($X$) based on the Pokémon's health, status, and the ball used. The closer $X$ is to 255, the higher your chance of success.
The Gen V Formula
The calculation performed by the game is roughly:
Modified Rate = [ (3 × MaxHP – 2 × CurrHP) × Rate × BallMod ] / (3 × MaxHP) × StatusMod
Where:
- MaxHP: The Pokémon's full health.
- CurrHP: The Pokémon's remaining health. Lower is better.
- Rate: The species-specific catch rate (e.g., 3 for most legendaries, 255 for weak Pokémon like Patrat).
- BallMod: The multiplier of the ball (e.g., Ultra Ball is 2.0).
- StatusMod: 2.5 for Sleep/Freeze, 1.5 for others.
Critical Capture Mechanics
Gen V introduced the Critical Capture mechanic. Occasionally, you will hear a distinct metallic sound when throwing the ball, and it will only shake once before clicking. The probability of a Critical Capture increases based on how many Pokémon you have registered in your Pokédex.
Tips for Maximum Success
- False Swipe is King: Reducing HP to 1 maximizes the "HP Factor" of the equation.
- Sleep vs. Paralysis: In Gen V, Sleep and Freeze provide a 2.5x multiplier, whereas Paralysis only provides 1.5x. Always prioritize Sleep (using moves like Spore or Hypnosis) for difficult catches.
- Dark Grass: Be careful in double battles (Dark Grass). You cannot throw a ball if there are two wild Pokémon on the field; you must faint one first.
- Dusk Balls: If you are playing at night or in a cave, Dusk Balls (3.5x) are significantly better than Ultra Balls (2x).
- Turn Count: If a battle drags on, Switch to Timer Balls. After turn 10, they reach a 4x multiplier, making them better than almost anything else.
Specific Catch Rates (Reference)
- Reshiram/Zekrom: Catch Rate 45 (Unusually high for legendaries, making them easier to catch for the story).
- Kyurem/Landorus/Thundurus: Catch Rate 3 (Standard difficult legendary rate).
- Victini: Catch Rate 3.
- Volcarona: Catch Rate 15.
Catch Probability:
100%
Master Ball ignores formula checks.
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resultDiv.style.display = 'block';
return;
}
// 4. Calculate Modified Catch Rate (X)
// Formula: X = (((3 * MaxHP – 2 * CurrentHP) * Rate * BallBonus) / (3 * MaxHP)) * StatusBonus
// Note: Gen V applies multipliers in specific order, usually ignoring floor during intermediate float steps in JS emulation,
// but to match game logic closer, we treat it continuously until the shake check.
// Apply Entralink Pass Power to the Ball Bonus effectively (or strictly to the final rate, usually multiplies catch rate)
// In Gen 5, Pass Power multiplies the capture rate.
var hpFactor = (3 * maxHP – 2 * currentHP);
var denominator = 3 * maxHP;
// Base X calculation
var modifiedRate = (hpFactor * speciesRate * ballBonus) / denominator;
// Apply Status
modifiedRate = modifiedRate * statusBonus;
// Apply Pass Power
modifiedRate = modifiedRate * passPower;
var catchPercentage = 0;
var shakeCheck = 0;
// 5. Determine Capture Probability
if (modifiedRate >= 255) {
catchPercentage = 100;
shakeCheck = 65536;
} else {
// Calculate Shake Probability (Y)
// Gen 5 Formula Approximation: B = 65536 / (255/X)^0.1875 <– This is for Gen 3/4
// Gen 5 actually uses: B = 65536 / (255/X)^0.25 (Fourth root approximation methodology)
// Actually, the exact logic is:
// if X < 255: B = floor(65536 / sqrt(sqrt(255/X)))
var a = 255 / modifiedRate;
var b = Math.sqrt(Math.sqrt(a)); // Fourth root
shakeCheck = Math.floor(65536 / b);
// Probability of passing one shake check (0 to 65535, needs to be 100) catchPercentage = 100;
// 6. Formatting Output
var percentString = catchPercentage.toFixed(2) + "%";
if (catchPercentage === 100) percentString = "100% (Guaranteed)";
var hpPercent = ((currentHP / maxHP) * 100).toFixed(1);
resultDiv.innerHTML = `
Capture Success Rate:
${percentString}
Debug Details:
HP Remaining: ${hpPercent}%
Modified Catch Rate (X): ${Math.floor(modifiedRate)}
Shake Threshold: ${shakeCheck} / 65536
Note: This calculates the probability per single throw.
`;
resultDiv.style.display = 'block';
}