Catching Pokémon is a core mechanic in the original Pokémon games (Red, Blue, and Yellow). The chance of successfully catching a wild Pokémon is determined by a complex formula that takes into account several factors. This calculator helps you understand your odds based on the game's mechanics.
The Catch Rate Formula (Generation 1)
The fundamental formula used in Gen 1 is as follows:
StatusFactor = 1 (No Status), 2 (Poison/Burn/Paralysis), or 3 (Sleep/Freeze)
LevelFactor = (2 * TargetLevel + 10) / 250 (Note: This is simplified for Gen 1, the actual game code uses a slightly different approach but this is a good approximation for understanding the impact)
The game then generates a random number between 0 and 255. If this number is less than or equal to the calculated CatchChance, the Pokémon is caught.
Factors Explained:
Base Catch Rate: Every Pokémon species has a hidden Base Catch Rate, ranging from 3 (Legendary Pokémon like Mewtwo) to 255 (common Pokémon like Rattata). This is a fundamental property of the Pokémon.
Target Pokémon's Level: While the direct impact of level is different in Gen 1 compared to later generations, a higher level Pokémon generally has a slightly lower chance of being caught if all other factors are equal due to how the formula is structured.
Target Pokémon's HP: This is crucial. The lower the current HP of the target Pokémon, the higher your catch chance. Catching a Pokémon with 1 HP is significantly easier than catching one at full health.
Status Condition: Inflicting a status condition (Sleep, Freeze, Paralysis, Poison, Burn) dramatically increases your catch rate. Sleep and Freeze offer the best bonus.
Ball Type: Different Poké Balls offer different multipliers. The standard Poké Ball has a 1x modifier, the Great Ball a 1.5x modifier, and the Ultra Ball a 2x modifier.
How to Use the Calculator:
Enter the Level of the Pokémon you are trying to catch.
Input the Base Catch Rate of the specific Pokémon species (you can find this on reliable Pokémon databases).
Enter the Max HP and Current HP of the wild Pokémon. For the best odds, try to lower its HP as much as possible without knocking it out.
Select the applicable Status Condition if the wild Pokémon is affected by Sleep, Freeze, Paralysis, Poison, or Burn.
Choose the Ball Type you are using (Poké Ball, Great Ball, or Ultra Ball).
Click "Calculate Catch Rate" to see your estimated chance of success.
Example Calculation:
Let's try to catch a wild Abra (Base Catch Rate: 200) at Level 15. Our Pikachu is Level 20 and has 70/70 HP. We've managed to lower the Abra's HP to 10 out of its Max HP of 50. Abra is currently Paralyzed. We are using a Great Ball.
Pokémon Level: 15
Base Catch Rate: 200
User Pokémon HP: N/A for this calculation
Max HP of Target Pokémon: 50
Current HP of Target Pokémon: 10
Status Condition: Paralysis (Modifier 2)
Ball Type: Great Ball (Modifier 1.5)
Using these values in the calculator will give you the estimated percentage chance of catching this specific Abra.
function calculateCatchRate() {
var pokemonLevel = parseFloat(document.getElementById("pokemonLevel").value);
var baseCatchRate = parseFloat(document.getElementById("baseCatchRate").value);
var userHP = parseFloat(document.getElementById("userHP").value); // Not directly used in Gen 1 catch formula but kept for user context
var maxHP = parseFloat(document.getElementById("maxHP").value);
var currentHP = parseFloat(document.getElementById("currentHP").value);
var statusCondition = parseInt(document.getElementById("statusCondition").value);
var ballType = parseFloat(document.getElementById("ballType").value);
var resultElement = document.getElementById("result");
resultElement.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(pokemonLevel) || isNaN(baseCatchRate) || isNaN(userHP) || isNaN(maxHP) || isNaN(currentHP) || isNaN(statusCondition) || isNaN(ballType)) {
resultElement.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (pokemonLevel <= 0 || baseCatchRate <= 0 || maxHP <= 0 || currentHP maxHP) {
resultElement.innerHTML = "Please enter valid positive values for levels and HP. Current HP cannot exceed Max HP.";
return;
}
if (baseCatchRate > 255) {
resultElement.innerHTML = "Base Catch Rate cannot exceed 255.";
return;
}
// Gen 1 Catch Rate Formula Implementation
// Note: The 'Level Factor' in Gen 1 is a bit more complex in the actual game code,
// involving specific checks against the user's Pokémon level and the target's stats.
// For a simplified and common interpretation used in many calculators, we can use a
// simplified level adjustment or even omit it if focusing purely on the core modifiers.
// Let's use a common approximation for Level Factor that influences the odds.
// A common approximation for the Level Factor in Gen 1 calculators:
// The actual game code has a more intricate calculation involving user's level,
// target's level, and other factors that can be quite complex to reverse engineer perfectly.
// For simplicity and common understanding, many calculators use a factor that generally
// slightly decreases catch rate with higher target levels, or a constant.
// A widely accepted simplified approach:
var levelModifier = (2 * pokemonLevel + 10) / 250;
// However, some sources suggest the level influence is minimal or handled differently.
// Let's stick to a common interpretation that includes level.
var hpFactor = (3 * maxHP – 2 * currentHP) * 100 / (3 * maxHP);
var statusFactor = statusCondition; // Already 0, 1, 2 in select options, matching formula needs (0 for none, 1 for sleep/freeze, 2 for poison/burn/paralysis) – wait, the formula uses 1, 2, 3. Let's adjust.
var statusMultiplier = 1;
if (statusCondition === 1) { // Sleep/Freeze
statusMultiplier = 2; // Common multiplier for Sleep/Freeze in Gen 1 calc approximations
} else if (statusCondition === 2) { // Poison/Burn/Paralysis
statusMultiplier = 1.5; // Common multiplier for Paralysis/Poison/Burn in Gen 1 calc approximations
}
var finalModifier = hpFactor * statusMultiplier * ballType / 100;
// The direct formula for catch chance is complex and involves multiple stages.
// A simplified, commonly used approach:
// Catch Rate = Base Catch Rate * (3*MaxHP – 2*CurrentHP) * Status Multiplier * Ball Multiplier / (3*MaxHP) / 255 * (2*Level + 10) / 250 * 100 ??? -> This gets convoluted.
// Let's use a more standard approach often seen in Gen 1 calculators that aims to approximate the outcome.
// The "shake" count is what the game calculates internally.
// A common formula for the value that is compared against a random number (0-255):
var catchValue = ( ( ( (3 * maxHP) – (2 * currentHP) ) * baseCatchRate * ballType ) / (3 * maxHP) ) * statusMultiplier;
// The level factor is debated, some use it, some don't significantly.
// A common approach that accounts for level somewhat:
var adjustedCatchValue = catchValue * ( (2 * pokemonLevel + 10) / 250 );
// The final comparison is against 255.
// The chance of success depends on this 'adjustedCatchValue' compared to a random number.
// A direct percentage is hard to give without simulating shakes.
// However, a common derived percentage is often presented.
// Let's calculate the raw "catch value" and then estimate a percentage.
// Simplified Percentage Calculation often seen:
// This is a derived percentage, not the direct in-game calculation of shakes.
var estimatedCatchChance = (adjustedCatchValue / 255) * 100;
// Ensure the chance doesn't exceed 100%
estimatedCatchChance = Math.min(estimatedCatchChance, 100);
// Ensure the chance isn't below 0% (though unlikely with positive inputs)
estimatedCatchChance = Math.max(estimatedCatchChance, 0);
resultElement.innerHTML = "Estimated Catch Chance: " + estimatedCatchChance.toFixed(2) + "%";
// Add a note about the complexity
resultElement.innerHTML += "Note: This is an estimation. Actual catch mechanics involve 'shakes' and can be influenced by other factors not fully represented here.";
}
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