Attacker's hash power (%):
Blocks to catch up:
Time ratio (κ):



This calculator shows the probability that an attacker with a given percentage of the total network hashrate could successfully reorganize z blocks, based on the conditional formula in Double Spend Races which includes κ (time ratio).

Parameters:

  • Attacker hashrate (% q): The portion of total network hashrate controlled by the attacker
  • Honest hashrate (% p): The portion controlled by honest miners (1 - q)
  • Blocks behind (z): How many blocks the honest chain is ahead.
  • Time ratio (κ):
    • If κ > 1, honest blocks took longer than average ⇒ attacker has higher chance.
    • If κ < 1, honest blocks were faster ⇒ lower attacker chance.
    • If κ=1, you ignore timing and assume an “average” scenario (Satoshi’s formula).