The terms sportsbooks use without explaining. Plain definitions, linked straight into the calculator that uses each one.
Three names for the same thing: the sportsbook's built-in margin. Add up the implied probability of every side of a market and it comes to more than 100% — usually 104-105% on a standard -110/-110 line, more on props and futures. That extra is the fee you pay to bet, win or lose.
Strip it out with the No-Vig Calculator.
The win chance a price represents on its own, before removing the vig. Positive American odds: 100 / (odds + 100). Negative odds: |odds| / (|odds| + 100). A -150 favorite implies a 60% win chance; that number still includes the book's cut.
Convert any price with the Odds Converter.
What's left after the vig is stripped out. Divide each side's implied probability by the sum of both sides' implied probabilities and the result rescales to exactly 100% — the market's honest opinion, not the price you're charged to access it.
This is the number every pick on this site is measured against. Calculate it here.
The win percentage you'd need at a given price just to come out flat, long run. It's mathematically the same figure as that price's implied probability — at -110 you need 52.4%, not 50%, just to break even.
Full breakdown on Tools.
The gap between the price you bet and the price at kickoff (the close). Books move lines toward where sharp money and late information push them, so the closing number is the market's best final estimate. Beating the close consistently — regardless of whether any individual bet wins — is the strongest evidence a betting process actually has an edge.
A formula for how much of a bankroll to risk on a bet with an edge, sized to maximize long-run growth without risking ruin. Full Kelly is aggressive and high-variance; most serious bettors use half or quarter Kelly instead.
Size a stake with the Kelly Calculator.
The average result of a bet if it were placed many times, given the true win probability and the price offered. A bet is +EV when the price pays out more than the true risk justifies — the only kind of bet that makes money over a large enough sample.
Run the numbers on the EV Calculator.
The vig on each leg of a parlay compounds instead of adding. A parlay that looks like a modest markup leg-by-leg can carry an effective hold several times higher than a straight bet once every leg's margin multiplies together — the single most underestimated cost in recreational betting.
See it compound on the Parlay Calculator.
A straight bet on which side wins, no spread involved. The price itself reflects each side's implied win probability — favorites carry negative odds, underdogs carry positive odds.
Points added to or subtracted from a team's final score to bring both sides closer to a coinflip in the book's pricing, typically offered near -110 on each side regardless of how lopsided the actual matchup is.
Betting the other side of a wager you already hold — usually after the line has moved in your favor — to lock in profit or cap a loss no matter how the game ends.
Model it on Tools.
"Sharp" money comes from bettors books treat as skilled — it can move a line sharply even on small volume. "Square" money is public, recreational volume that books shade lines toward, since it's larger and more predictable in aggregate.