Understand a drop chance
Choose a chest or monster, the reward you want and a number of attempts. For an ordinary table draw, the reward’s weight is divided by the full table weight. A monster’s separate chance to roll that table also applies.
The main result is the probability of at least one successful drop across independent attempts. An expected count is an average over repeated runs, not a guarantee for your next run.
The displayed calculations use base probabilities. A quantity range describes items awarded by a successful outcome; it is not a second probability. Kill speed and player-specific effects are not guessed.
Why a rare drop can take longer than average
With independent draws, earlier failures do not increase the chance of the next draw. Enter the size of the new run you are planning; the result is not a countdown to a guaranteed reward.
A probability target is not a guarantee. The average is not a deadline.
Plan by probability, not a promise
- Openings
- 500
- No drop yet
- 17.35%
- Average openings to first drop
- 286
- Chance per opening
- 1 in 286
Sources
Count chests actually opened, not the quantity requested in the bank. If the bank fills, the game stops opening and retains the next rolled item for that chest. Free space first; this planner does not simulate that already rolled item.
Ordinary base loot-table draws. Scripted rewards, item conversion, doubling and lost loot are not simulated.
