Drop Chance Calculator

Written byOleh Soloninupdated 10 September 2026

Chance per attempt, %

Number of attempts

Confidence wanted, %

Result

At least one, %63.4%
None at all, %36.6%
Expected items1
Average attempts per item100
Median attempts69
Attempts for that confidence298

A one percent chance is not a hundred attempts

Drop chance calculator: the probability of getting an item at least once in a run of attempts, the chance of getting nothing, the average and median number of tries, and how many attempts you need to be 90 or 95 percent sure.

Intuition says a one percent drop takes a hundred attempts. It does not: the chance of getting it at least once in a hundred is about 63 percent. More than a third of the time, a hundred attempts ends with nothing.

The reason is independence. The correct formula counts failure rather than success: multiply the chances of missing and subtract from one. The median falls out of the same arithmetic — the number of attempts at which half of all players have it.

What this calculator shows

The chance of at least one drop across a run of attempts
The mean and median number of attempts per item
How many attempts a given confidence level requires

What to keep in mind

Attempts are treated as independent: the chance does not rise with failures. Games with a pity system break that, and have their own calculation.
The stated rate is taken at face value; developers sometimes apply undocumented modifiers.

FAQs

What are the odds of a 1% drop in 50 tries?

About 39.5%: the chance of missing all fifty is 0.99⁵⁰ ≈ 0.605. In 100 tries it rises to 63.4%, in 200 to 86.6%, and it takes 459 tries to reach 99%.

How many runs does a 0.5% drop take?

On average 200, but the median is 139 — half of all players have it by then — and being 95% sure takes 598 runs. Small chances stretch the tail: the unluckiest fifth of players are still farming after 320.

Why can a 1% drop not appear in a hundred tries?

Because each attempt is independent. The chance of missing a hundred times running is 0.99 to the hundredth power — about 37 percent.

How do I calculate the chance of at least one success?

One minus the failure chance raised to the number of attempts. For one percent over a hundred tries: 1 − 0.99¹⁰⁰ = 0.634.

What is the median number of attempts?

The point where the chance of success reaches fifty percent. At one percent that is 69 attempts, not a hundred.

Does the chance improve after a losing streak?

Without a pity system, no. Dice do not remember previous rolls, and ten failures do not make the eleventh attempt luckier.

Worked example

A hundred attempts at one percent

Input: 1% chance, 100 attempts, 95% confidence

Output: 63.4% for at least one; 95% confidence needs 298 attempts

Note: The median here is 69 attempts: half of all players have it sooner, half later. And being nearly certain takes three times the 'intuitive' hundred.

Useful links

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Drop Chance Calculator

Result

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