How to use this calculator
This model assumes independent fixed-rate attempts at a fixed price. The average cost assumes you keep trying until a first success; it is not a prediction of your individual spending. Your budget is converted into a whole number of affordable attempts by rounding down. The chance of no success remains important even when the expected success count is one or more. This tool does not include resale value, taxes or fees.
The formula
Expected cost to first success = cost / p
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% and 3 per attempt, the average cost to first success is 300; that is not a safe budget.
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.