In Hand Salary Calculator

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Reviewed by Dr. Sarah Jenkins, Statistician & Game Mechanics Expert | Last Updated: October 2023
Use this Drop Chance Calculator to determine the probability of obtaining a specific item (loot) after a set number of attempts (runs). Input your drop rate percentage and the number of times you plan to farm the item to see your cumulative success chance.

Drop Chance Calculator

The percentage chance to get the item in a single run.
How many times you will attempt the activity.
Probability of at least one drop:
0%

Drop Chance Formula

The calculation is based on the Binomial Probability formula, specifically finding the probability of the event happening at least once ($P \ge 1$).

P = 1 – (1 – p)n

Where:

  • P is the probability of getting the item at least once.
  • p is the drop rate per single attempt (expressed as a decimal).
  • n is the number of attempts (runs).

Source: Wikipedia: Binomial Distribution

Variables Explanation

  • Drop Rate (%): This is the likelihood of the item dropping in one singular event (kill, chest open, etc.). For example, a “1 in 100” chance is 1%.
  • Number of Runs: The total count of independent trials you intend to perform.

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What is a Drop Chance Calculator?

A Drop Chance Calculator is a statistical tool used primarily by gamers (in MMORPGs like WoW, RuneScape, or gacha games like Genshin Impact) to understand the realities of Random Number Generation (RNG). It answers the question: “If an item has a 1% drop rate, and I kill the boss 100 times, what are my chances of actually getting it?”

Many players mistakenly believe that 100 runs at a 1% drop rate guarantees a drop (100 * 1% = 100%). However, probability works differently. Because each event is independent, the actual chance is approximately 63.2%, not 100%. This tool helps manage expectations for farming rare items.

How to Calculate Drop Chance (Example)

Let’s say you are farming a mount with a 5% drop rate and you plan to do 20 runs.

  1. Convert the percentage to a decimal: 5% = 0.05.
  2. Calculate the chance of failure for one run: 1 – 0.05 = 0.95.
  3. Calculate the chance of failing all 20 runs: 0.9520 ≈ 0.358 (35.8%).
  4. Subtract the failure chance from 1 to find the success chance: 1 – 0.358 = 0.642.
  5. Result: You have a 64.2% chance of seeing the drop at least once.

Frequently Asked Questions (FAQ)

Why is the result never 100%?
In probability, unless the drop is guaranteed (scripted), there is always a tiny mathematical chance that you fail every single time, no matter how many runs you do. The number gets closer to 100%, but never truly touches it.

What is a “Dry Streak”?
A dry streak occurs when a player goes significantly over the expected number of runs without getting the drop. Statistically, this is bound to happen to a percentage of the player base.

Does luck increase with more attempts?
No. This is known as the “Gambler’s Fallacy.” The game does not “remember” your previous failures. Your 100th attempt has the exact same drop rate as your 1st attempt.

Is 50% drop rate the same as a coin flip?
Yes. A 50% drop rate is exactly like flipping a coin. Getting the item is Heads; not getting it is Tails.

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