This calculator helps you estimate the number of pulls you might need to get a specific character or item in a gacha game, based on the advertised rates. Understanding these probabilities can help manage your in-game currency and expectations.
e.g., 1 (for one ticket or premium currency unit)
e.g., 0.5 for a 0.5% chance
e.g., 10 for a 10% chance (if applicable, like for a 3-star item)
e.g., 90 (the number of pulls after which you're guaranteed the item)
e.g., 2 (the increase in rate per pull after reaching a certain point before pity)
.gacha-calculator-container {
font-family: sans-serif;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
.gacha-calculator-title {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.gacha-calculator-description {
color: #555;
font-size: 0.9em;
text-align: justify;
margin-bottom: 20px;
line-height: 1.5;
}
.gacha-calculator-inputs {
margin-bottom: 20px;
display: grid;
grid-template-columns: 1fr;
gap: 15px;
}
.gacha-input-group {
display: flex;
flex-direction: column;
}
.gacha-input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.gacha-input-group input[type="number"] {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
.gacha-input-group small {
color: #777;
font-size: 0.8em;
margin-top: 3px;
}
.gacha-calculate-button {
display: block;
width: 100%;
padding: 12px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
}
.gacha-calculate-button:hover {
background-color: #0056b3;
}
.gacha-calculator-result {
margin-top: 20px;
padding: 15px;
border: 1px solid #e0e0e0;
background-color: #fff;
border-radius: 5px;
text-align: center;
font-size: 1.1em;
color: #333;
min-height: 50px;
display: flex;
align-items: center;
justify-content: center;
}
function calculateGachaPulls() {
var pullCost = parseFloat(document.getElementById("pullCost").value);
var targetRate = parseFloat(document.getElementById("targetRate").value) / 100; // Convert percentage to decimal
var guaranteedRate = parseFloat(document.getElementById("guaranteedRate").value) / 100; // Convert percentage to decimal
var pityCount = parseInt(document.getElementById("pityCount").value);
var pityRateIncrease = parseFloat(document.getElementById("pityRateIncrease").value) / 100; // Convert percentage to decimal
var resultElement = document.getElementById("gachaResult");
resultElement.innerHTML = ""; // Clear previous results
if (isNaN(pullCost) || isNaN(targetRate) || isNaN(guaranteedRate) || isNaN(pityCount) || isNaN(pityRateIncrease) ||
pullCost <= 0 || targetRate <= 0 || guaranteedRate < 0 || pityCount <= 0 || pityRateIncrease < 0) {
resultElement.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// — Basic Probability Calculation (Ignoring Pity for a moment) —
// The probability of *not* getting the item in one pull.
var probNotGettingItem = 1 – targetRate;
// Expected number of pulls to get the item if rates were constant.
// This is a simplified view using expected value E = 1/p
var expectedPullsSimple = 1 / targetRate;
// — Advanced Calculation considering Pity and Rate Increase —
// We need to simulate or calculate the probability distribution, which is complex.
// A common approach is to calculate the *cumulative probability* of getting the item by a certain pull count.
// We'll use a simplified approach that considers the increased rate near pity.
var currentRate = targetRate;
var pulls = 0;
var totalCost = 0;
var probabilityOfNotGetting = 1.0;
var estimatedPulls = 0;
// Calculate probability of NOT getting the item for pulls *before* pity triggers rate increase significantly
var pullsBeforePityRateIncrease = pityCount – Math.floor(pityCount / 10); // Assume rate increase starts roughly 10% before pity
if (pullsBeforePityRateIncrease < 0) pullsBeforePityRateIncrease = 0;
for (var i = 0; i = 1) break; // Already guaranteed or extremely likely
probabilityOfNotGetting *= (1 – targetRate);
pulls++;
}
// Calculate for pulls approaching pity where the rate increases
var pullsUntilPity = pityCount – pulls;
for (var i = 0; i = 1) break; // Already guaranteed or extremely likely
var effectiveRate = targetRate + (i * pityRateIncrease); // Simple linear increase for approximation
if (effectiveRate > 1) effectiveRate = 1; // Cap at 100%
probabilityOfNotGetting *= (1 – effectiveRate);
pulls++;
}
// If pity is reached and we still haven't got it, the probability of getting it in the next pull is effectively 100% (or very high due to pity mechanics).
// We need to check if probabilityOfNotGetting is still very close to 1.
if (probabilityOfNotGetting > 0.01) { // If there's still a significant chance we haven't gotten it by pityCount
probabilityOfNotGetting *= (1 – guaranteedRate); // Account for the guaranteed pull at pity
pulls++;
}
// If the item wasn't obtained by the guaranteed pity pull, we are essentially starting over with base rates, but the simulator has tracked it.
// The logic above is a simplification. A true simulation would run many trials.
// For this calculator, we'll estimate based on the average.
// A more robust way is to consider the expected number of pulls considering pity.
// The probability of NOT getting the item by pull N is P(not by N) = product[(1-rate_i) for i=1 to N]
// The expected pulls is approximately Sum[ P(not by N) for N=0 to infinity ]
var cumulativeProbNotGetting = 1.0;
var estimatedPullsForTarget = 0;
var maxPullsToSimulate = pityCount * 5; // Simulate a reasonable number of pity cycles
for (var i = 1; i <= maxPullsToSimulate; i++) {
var currentPullRate;
if (i = pityCount – Math.floor(pityCount / 10) && pityCount > 10) { // Apply pity rate increase
currentPullRate = Math.min(1.0, targetRate + (i – (pityCount – Math.floor(pityCount / 10))) * pityRateIncrease);
}
} else {
currentPullRate = guaranteedRate; // This is the rate at pity, often effectively 100% for the banner item
if (i > pityCount) { // If we passed pity, it means we didn't get it, and likely reset. However, the calculation needs to converge.
// In many games, pity resets. The probability of getting the item on pull `pityCount + 1` is extremely high if not obtained earlier.
// For simplicity, we assume the worst case where you hit pity.
currentPullRate = targetRate; // Assuming base rate after pity reset for subsequent cycles
// To simplify: we will just calculate the chance of getting it UP TO the pity threshold.
}
}
// Probability of NOT getting it on THIS specific pull
var probNotGettingThisPull = 1 – currentPullRate;
// Probability of NOT getting it by the end of THIS pull
cumulativeProbNotGetting *= probNotGettingThisPull;
// Add the probability of needing this many pulls (which is the probability of NOT getting it in previous pulls)
estimatedPullsForTarget += cumulativeProbNotGetting;
if (cumulativeProbNotGetting < 0.0001) { // If probability of not getting it becomes negligible, stop simulation
break;
}
}
// The result `estimatedPullsForTarget` is now the expected number of pulls.
// We add 1 to account for the final pull that would succeed.
estimatedPullsForTarget += 1;
// Ensure the estimated pulls are at least the pity count in worst case scenario
if (estimatedPullsForTarget < pityCount && targetRate < 1) {
estimatedPullsForTarget = pityCount;
}
var totalCostEstimate = estimatedPullsForTarget * pullCost;
var outputHTML = "Estimated pulls needed to obtain the target item: " + estimatedPullsForTarget.toFixed(2) + "";
outputHTML += "Estimated cost in currency: " + totalCostEstimate.toFixed(2) + "";
outputHTML += "Note: This is an estimate based on average probabilities and common pity mechanics. Actual results may vary significantly due to luck.";
resultElement.innerHTML = outputHTML;
}