Existing Bet Calculator

Existing Bet Calculator Info

If you are considering a new bet whose outcome changes the probability of an existing bet, the existing bet calculator will show you how much to wager while maximizing the expected growth of your bankroll. Note that if you are betting on the same side or opposite side of an existing bet you likely want to use the Same Side Kelly Calculator or Opposite Side Kelly Calculator instead.

Odds: The odds of the new bet.
Probability: The probability the new bet wins.
Payout: The payout of the existing bet as a percentage of your bankroll.
Existing Bet Probability if Hedge Wins: The updated probability of the existing bet if the hedge wins.
Existing Bet Probability if Hedge Loses: The updated probability of the existing bet if the hedge loses.
Odds Format: Specifies the format used in odds fields.

Math

f = p (1 + w)^{{p^{'}}_{e}} - \frac{q}{b} (1 + w)^{p_{e}}

f: The fraction of your bankroll to bet.
p: The probability the new bet wins.
w: The fraction of your bankroll represented by your existing bet.
q: The probability the new bet loses.
b: The net fractional odds of the new bet.
p_e: The probability the existing bet wins if the hedge wins.
p^'_e: The probability the existing bet wins if the hedge loses.

Book Links

But How Much Did You Lose? (chapter 2)

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