Grind Session Tracker
Log the runs, keep the odds honest, and know when a dry streak is genuinely unusual rather than just annoying.
BFCBrilliance · bfcbrilliance.com/tools/drop-chance-calculator
The hunt
- Game
- Item
- Source
- Drop rate
- Started
- Rate source (wiki / patch notes)
Log the runs
| Date | Runs this session | Running total | Drops | Notes |
|---|---|---|---|---|
The maths
- Chance of nothing in n tries
- (1 - rate) ^ n
- Chance of at least one
- 1 - (1 - rate) ^ n
- Drops expected
- rate x attempts
- 1% drop, 100 tries
- about 63%, not 100%
- Tries for a coin-flip chance
- log(0.5) / log(1 - rate)
- Tries for a 90% chance
- log(0.1) / log(1 - rate)
- Does NOT apply to
- pity and bad-luck protection
Before a long grind
- Rate confirmed from the wiki or patch notes, not a forum guess
- Checked whether the rate changed in a recent patch
- Checked for a pity or bad-luck system - it changes everything
- Checked whether difficulty, luck stats or level affect the rate
- Confirmed the source actually drops it in this mode
- Worked out the 90% point before starting, so you know the shape of it
- Decided in advance when you stop
A dry streak is not evidence
Each attempt rolls fresh and the game does not remember the last two hundred. Ten percent of players will still be empty-handed at the 90% mark, and that is not bad luck, it is what 90% means. Judge it by the still-having-none figure: worth a second look when it is well under one percent, not before.