This calculator is arithmetic on a table, not a live mixer. Enter quantities from your own Backseat Rally session. It will not click the shop.
Drop probability
At least one Epic crate
Estimates the chance of opening at least one Epic when every crate is an independent roll. Clubman's listed Epic chance is 8.5 percent, Wheel is 13.5 percent, and Works is 17 percent. Type the chance from the crate you are buying. This does not include the guarantee that the next crate is Epic or better after 12 misses, and it does not separate Legendary from Epic.
Chance of at least one success = 1 − (1 − chance per attempt) raised to the number of attempts.
Default 8.5 is the Clubman Epic chance. Change it for Wheel or Works. Pity after 12 non-Epic crates is a different rule and is not applied here.