Drop Rate Calculator

Calculate the chance of getting at least one item from a drop rate and a number of attempts.

Chance of Getting at Least One Chance of getting none:

Expected drops:

Attempts Needed to Reach a Target Chance

What is the Drop Rate Calculator?

This tool calculates the chance of getting an item at least once, the chance of getting none, and the expected number of drops from an item's drop rate and the number of attempts. It's useful for game developers designing reward rates and estimating how many runs a reward will take.

How to Use

Enter the item's drop rate as a percentage.
Enter the number of attempts, as a whole number of 1 or more.
Press "Calculate".
Check the three results and the number of attempts needed for each target chance.

Example

With a 5% drop rate and 20 attempts, the chance of getting at least one item is about 64.15%, the chance of getting none is about 35.85%, and the expected number of drops is 1.00.

Using This in Game Development

When designing loot tables or quest rewards in Unity, this helps you see roughly how many runs a player needs before a reward becomes likely. It's also a way to balance how difficult a rare item feels, using both its chance and the expected number of attempts.

Notes

This calculation assumes every attempt is independent and uses the same drop rate. It does not account for pity systems, drop rate boosts, multiple items dropping at once, or per-player adjustments. If you want to check the odds for a loot table made of several items, use the Loot Table Calculator. The expected number of drops is an average — it does not guarantee how many items you'll actually get.

FAQ

If the drop rate is 5%, am I guaranteed one after 20 attempts?

No. The chance of getting at least one in 20 attempts is about 64.15%, and there is still about a 35.85% chance of getting none.

What does "expected number of drops" mean?

It's the average number of items you'd get if you repeated the same attempts many times. For a 5% rate over 20 attempts, that average is 1.00 — but it doesn't mean you'll always get exactly one.

Can I still get nothing after 100 attempts?

Yes. As long as the drop rate is above 0% and below 100%, there is always some chance of getting nothing, however small.