How to use this calculator
This calculator treats each ticket as equally likely and removes each winning ticket before the next draw. The same person may win more than once if different tickets win. If the rules remove all of a person’s tickets after a win, or give different weights to different entries, these results do not apply. Include your tickets in the total; use the final entry count for a final probability.
The formula
1 − C(N − K,d) / C(N,d)
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
With 5 of 500 tickets and 3 winning draws, the chance of at least one prize is about 2.98%.
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.