Calculation method
The selected reroll changes each die???success chance, then the tool recalculates the pool. It provides defined rules instead of claiming every custom reroll.
Assumptions and limits
This is a tabletop design scenario using your inputs, not a prediction of player experience. Check your game???exact rules and edge cases before finalizing a design.
Related tools
Define exactly what is rerolled
The initial success chance, number of dice, and reroll rule determine whether a reroll affects failures, every die, or a limited subset. Read the result as the probability after the stated reroll condition, not as a universal advantage value.
Use the result in a design decision
Compare one reroll with an extra die at the same target. They can feel different even when their success chances are similar because rerolls change a failed moment while extra dice change the initial pool.