Item Probability Calculator Gacha & Drop Rates

Tool

About

This free online Item Probability Calculator helps you determine the likelihood of obtaining specific items from gacha systems, loot boxes, or any scenario with a known drop rate. The core principle behind this calculator is based on the concept of complementary probability. If 'p' is the individual probability of an item dropping in a single attempt, then '1-p' is the probability of *not* getting the item in one attempt. For 'n' attempts, the probability of *not* getting the item in any of those 'n' attempts is (1-p)^n. Therefore, the probability of getting *at least one* of the desired items in 'n' attempts is calculated as `1 - (1-p)^n`. This client-side tool instantly computes this probability along with the total expenditure, making it ideal for gamers, developers, or anyone analyzing random drop mechanics in games or similar systems.