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Item Drop Grind Runs Calculator

Runs needed for a target probability of at least one drop.

Compute the number of runs needed in a video-game farming loop to reach a target probability of seeing at least one drop, given the per-run drop rate: n = ln(1 − target_p) / ln(1 − drop_p).

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

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Results

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

n = ln(1 − P_target) / ln(1 − p)

In depth

Compute the number of runs needed in a video-game farming loop to reach a target probability of seeing at least one drop, given the per-run drop rate: n = ln(1 − target_p) / ln(1 − drop_p).