How to use this calculator
Enter a percentage for a single independent attempt. The result measures the chance of one or more successes, not the chance on the next attempt. A long dry streak does not increase your next chance when the rate stays fixed. This is a reward-drop calculator, not a medical drip-rate tool. For a rate that changes after misses, use the pity calculator instead.
The formula
1 − (1 − p)ⁿ
Here p is a probability from 0 to 1, n is a whole number of attempts, C(a,b) counts combinations, and ∏ means multiply all the factors. The input labels define the other symbols.
A worked example
At 1% per attempt, 100 tries give a 63.40% chance of at least one drop.
Does this predict what I will get?
No. It describes a probability under the rules you enter. A single run can differ from the average. A displayed rounded 100% may still be slightly below certainty unless the model includes a guarantee.
Where do the rates come from?
You enter them. Check the rules and rate disclosure for your exact outcome. We do not supply odds for real products, collect account details or fetch rates from a game or seller.