Betting Calculators
Free tools to calculate expected value, convert odds formats, strip the vig, size bets with Kelly Criterion, build parlays, and hedge your bets.
Calculate the expected value of any bet given true probability and offered odds.
The sharp / no-vig probability of winning this bet
The odds offered by the sportsbook — e.g. +120 or -110
Formula
EV% = (Win Probability × Decimal Odds − 1) × 100
Expected Value (EV)
The average outcome per bet over a large sample. Positive EV means you have a mathematical edge over the sportsbook.
Vig / Juice
The sportsbook's built-in profit margin. −110/−110 standard lines carry ~4.55% vig. Zero-vig lines reflect true probability.
Kelly Criterion
A bankroll formula that sizes bets to maximise long-run growth. Half-Kelly (50% of full stake) reduces variance significantly.
Parlay
A combined bet where all selections must win. Payouts multiply with each leg, but so does risk — one loss kills the entire bet.
Hedge Betting
A risk management strategy that places a second bet on the opposite outcome to lock in guaranteed profits or limit losses.