Calculate the math before you place the bet

Split stakes across two outcomes, see whether a true arb exists, and size each leg to lock the same payout.

Margin = 1 - (1/odds A + 1/odds B)

Estimate whether a single bet is worth taking by combining probability, odds, and stake into EV and ROI.

EV = p(win) x profit - p(loss) x stake

Model how much cash a stake-not-returned bonus bet converts into after lay odds and exchange commission.

Lay stake = bonus x (back odds - 1) / (lay odds - commission)

Size into edge with discipline by converting your bankroll, edge, and price into a percentage stake recommendation.

Kelly = ((odds - 1) x p - q) / (odds - 1)

Spread one budget across multiple outcomes while targeting the same gross payout on each result.

Stake_i = bankroll x (1/odds_i) / sum(1/odds)

Convert between decimal, fractional, American, and implied probability formats instantly.

Decimal = numerator / denominator + 1

Calculate the combined odds, implied probability, and expected value of a same game multi (parlay) across multiple legs.

Combined odds = odds_1 x odds_2 x ... x odds_n