The mechanics of catching a Pokémon are governed by a specific mathematical formula introduced in the early generations and refined over time. Our calculator uses the standard capture formula to determine the likelihood of a successful catch.
Max HP vs Current HP: Lowering a Pokémon's health significantly increases the catch value. Reducing a target to 1 HP using moves like False Swipe is the most effective strategy.
Base Catch Rate: Every species has a fixed number between 1 and 255. Rare legendaries like Mewtwo or Rayquaza usually have a rate of 3, while common Pokémon like Caterpie have a rate of 255.
Ball Multiplier: Different Pokéballs provide different modifiers. An Ultra Ball is twice as effective as a standard Poké Ball, while specialized balls like the Net Ball or Dusk Ball can provide even higher modifiers under specific conditions.
Status Conditions: Sleep and Freeze are the most effective (2x multiplier), while Paralysis, Poison, and Burn provide a smaller boost (1.5x multiplier).
Common Pokémon Catch Rates
Pokémon Category
Base Catch Rate
Difficulty
Legendary Pokémon
3
Extremely Hard
Pseudo-Legendaries (Beldum)
3-45
Very Hard
Starters / Rare Encounters
45
Hard
Common Evolutions
75-120
Moderate
Basic Wild Pokémon
190-255
Easy
Capture Example
Imagine you are trying to catch Mewtwo (Base Rate: 3) with an Ultra Ball (2x multiplier). Mewtwo has 200 Max HP, and you have reduced it to 10 HP. It is currently Paralyzed (1.5x multiplier).
Using the formula: a = (((3*200 - 2*10) * 3 * 2) / (3*200)) * 1.5
The result is a catch probability of approximately 1.45% per throw. This demonstrates why catching legendary Pokémon often requires dozens of turns and many items!
function calculateCatchChance() {
var maxHP = parseFloat(document.getElementById('maxHP').value);
var currentHP = parseFloat(document.getElementById('currentHP').value);
var baseRate = parseFloat(document.getElementById('baseCatchRate').value);
var statusMod = parseFloat(document.getElementById('statusBonus').value);
var ballMod = parseFloat(document.getElementById('ballBonus').value);
var levelMod = parseFloat(document.getElementById('levelMod').value);
if (isNaN(maxHP) || isNaN(currentHP) || isNaN(baseRate)) {
alert("Please enter valid numerical values for HP and Catch Rate.");
return;
}
if (currentHP > maxHP) {
alert("Current HP cannot be greater than Max HP.");
return;
}
// Capture Value formula 'a'
// a = (((3 * Max HP – 2 * Current HP) * Catch Rate * Ball Mod) / (3 * Max HP)) * Status Mod
var a = (((3 * maxHP – 2 * currentHP) * baseRate * ballMod) / (3 * maxHP)) * statusMod;
// Apply level modifier (simplified abstraction)
a = a * levelMod;
var finalPercentage;
if (ballMod === 255) {
finalPercentage = 100; // Master Ball
} else if (a >= 255) {
finalPercentage = 100;
} else {
// In modern games, if a 100) finalPercentage = 100;
if (finalPercentage < 0) finalPercentage = 0;
var resultDiv = document.getElementById('poke-result-area');
var probDiv = document.getElementById('captureProbability');
var shakeDiv = document.getElementById('shakeProbability');
resultDiv.style.display = 'block';
probDiv.innerHTML = "Estimated Catch Chance: " + finalPercentage.toFixed(2) + "%";
// Calculate expected number of balls
var expectedBalls = finalPercentage > 0 ? Math.ceil(100 / finalPercentage) : "Infinite";
shakeDiv.innerHTML = "On average, you will need " + expectedBalls + " successful throw(s) of this type to guarantee a catch.";
// Smooth scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}