function addDiscovery(amount) {
var input = document.getElementById('erBonusDiscovery');
var currentVal = parseInt(input.value) || 0;
if (amount === -1000) {
input.value = 0;
} else {
input.value = currentVal + amount;
}
}
function calculateDropChance() {
// 1. Get Inputs
var baseRate = parseFloat(document.getElementById('erBaseRate').value);
var arcane = parseInt(document.getElementById('erArcane').value);
var bonus = parseInt(document.getElementById('erBonusDiscovery').value);
var attempts = parseInt(document.getElementById('erAttempts').value);
// 2. Validate Inputs
if (isNaN(baseRate) || baseRate < 0) {
alert("Please enter a valid Base Drop Rate.");
return;
}
if (isNaN(arcane)) arcane = 10;
if (isNaN(bonus)) bonus = 0;
if (isNaN(attempts) || attempts 100) adjustedRate = 100;
// 5. Logic: Calculate Probability over N attempts (Binomial Distribution logic)
// P(At least one drop) = 1 – (Probability of Failure)^Attempts
// Probability of Failure = 1 – (Adjusted Rate / 100)
var probFailure = 1 – (adjustedRate / 100);
var probSuccessTotal = 1 – Math.pow(probFailure, attempts);
// 6. Logic: Estimated Kills for Confidence Intervals
// N = log(1 – Confidence) / log(FailureRate)
// If adjustedRate is 0 or 100, handle manually to avoid Infinity
var kills50, kills90, kills99;
if (adjustedRate = 100) {
kills50 = 1;
kills90 = 1;
kills99 = 1;
} else {
kills50 = Math.ceil(Math.log(1 – 0.50) / Math.log(probFailure));
kills90 = Math.ceil(Math.log(1 – 0.90) / Math.log(probFailure));
kills99 = Math.ceil(Math.log(1 – 0.99) / Math.log(probFailure));
}
// 7. Display Results
document.getElementById('resDiscovery').innerText = totalDiscovery.toFixed(1);
document.getElementById('resPerKill').innerText = adjustedRate.toFixed(3) + "%";
document.getElementById('resNumAttempts').innerText = attempts;
document.getElementById('resTotalProb').innerText = (probSuccessTotal * 100).toFixed(2) + "%";
document.getElementById('res50').innerText = kills50 + " kills";
document.getElementById('res90').innerText = kills90 + " kills";
document.getElementById('res99').innerText = kills99 + " kills";
// Show result box
document.getElementById('erResults').style.display = 'block';
}
Mastering Drop Rates in The Lands Between
Farming for specific weapons, armor sets, or crafting materials in Elden Ring requires more than just patience; it requires an understanding of the underlying mathematics of the game's RNG (Random Number Generation). This Elden Ring Drop Rate Calculator helps you determine your actual chances of finding that elusive Noble's Slender Sword or Magma Blade based on your character's stats and gear.
How Discovery Affects Drop Rates
In Elden Ring, your likelihood of finding an item is governed by the Discovery stat. Every enemy drop has a "Base Drop Rate" programmed into the game files. Your Discovery stat acts as a multiplier to this base rate.
The formula for calculating your adjusted drop chance is:
Adjusted Rate = Base Rate × (Discovery / 100)
For example, if an item has a 0.5% base drop rate and you have 200 Discovery:
Multiplier = 200 / 100 = 2.0x
New Drop Rate = 0.5% × 2.0 = 1.0%
Maximizing Your Discovery Stat
To reduce the time spent farming, you should maximize your Discovery before starting a farming run. Discovery is calculated as:
100 (Base) + Arcane Level + Equipment Bonuses
Source
Bonus Discovery
Notes
Arcane Stat
+1 per Level
Hard cap at 99 Arcane.
Silver Scarab
+75
Talisman found in Hidden Path to the Haligtree.
Silver-Pickled Fowl Foot
+50
Consumable item. Lasts 3 minutes.
Silver Tear Mask
+8
Increases Arcane by 8 (effectively +8 Discovery).
Marika's Soreseal
+5
Increases Arcane by 5.
The Probability of Success (Binomial Distribution)
Many Tarnished fall victim to the "Gambler's Fallacy," believing that if an item has a 1% drop rate, killing 100 enemies guarantees a drop. This is incorrect. Probability works differently.
The calculation used in this tool determines the probability of getting at least one drop over a set number of kills. Even with a 1% chance, after 100 kills, you only have a 63.4% chance of seeing the item. To reach a 99% certainty, you would need significantly more attempts.
Farming Tips
Re-spec for Farming: If you are farming an extremely rare item (like the Cleanrot Spear), consider using a Larval Tear to temporarily boost your Arcane to 99.
Fast Travel Reset: Find a site of grace close to your target. Kill the target, check for the drop, and immediately fast travel back to the grace to reset the enemy and save time walking.
Don't Forget the Fowl Foot: The Silver-Pickled Fowl Foot provides a massive +50 boost. However, teleporting removes the buff, so only use it if you can run back to the grace without warping.