Betting calculators for clearer odds, payouts, and stake decisions

They are three ways to write the same price. American odds use plus/minus numbers (for example +150 or -110). Decimal odds show total return per $1 staked (for example 2.50). Fractional odds show profit relative to stake (for example 3/2). Most payout math converts everything to decimal first.

Implied probability is the break-even win rate baked into a price: 1 ÷ decimal odds. At -110 (about 1.91 decimal), you need roughly 52.4% wins over time just to break even before considering other costs.

Vig (or juice) is the bookmaker’s margin built into prices. Hold (or overround) is how much the market’s implied probabilities exceed 100% when you add both sides. Higher hold usually means a tougher market for bettors; negative hold can signal an arbitrage opportunity across prices.

No-vig fair odds remove the bookmaker margin from a two-way market and renormalize each side so the probabilities total 100%. The result is an estimate of the market’s fair price before juice — useful as a baseline before you compare your own forecast.

Expected value is the average profit or loss if you could place the same bet many times at the same price with a correct win probability. Positive EV means the bet is profitable in the long run if your probability estimate is right; it does not guarantee any single wager wins.

Kelly is a stake-sizing rule that recommends a bankroll fraction based on your edge and the offered odds. Full Kelly maximizes long-run growth under ideal assumptions; many bettors use a fraction (for example quarter Kelly) to reduce variance and estimation error.

A parlay combines multiple legs into one bet that pays only if every leg wins. Use the Parlay Calculator to multiply leg prices into combined odds, then see profit and total payout for your wager — especially helpful before you place 2–15 leg tickets.

A round robin builds every parlay of a chosen size from a larger set of legs (for example all 3-leg parlays from five games). Use it when you want combination coverage instead of one all-or-nothing parlay, and need total risk and max return before committing.

Use it when you have a fair win probability (from a model or your own estimate) and want to know whether a sportsbook price is +EV or −EV in dollars. It answers “is this bet valuable?” before you decide stake size.

Use Kelly after you believe a bet is +EV and need a disciplined stake. It turns edge and odds into a suggested bankroll percentage so you avoid overbetting a single opinion.

Use it to balance stakes on opposite outcomes so both sides return the same payout. That can lock a guaranteed arbitrage profit when prices allow it, or show the cost of hedging an existing bet.

Use it when you have a stake-not-returned bonus (free bet) and want to know how much cash you can lock in by betting the bonus on one side and hedging with real money on the other — plus the conversion percentage.

Use it anytime you need to translate between American, decimal, and fractional formats, or quickly see break-even probability, profit, and total payout for a single price and stake.

Use it to focus on what a price requires you to win — the break-even percentage — before comparing that figure to your own forecast or a no-vig fair probability.

Use it on a two-way market when you want the book’s juice stripped out so you can see each side’s fair probability and fair American odds as a cleaner comparison point.

Use Hold or Vig to measure how expensive a two-outcome market is. Enter both sides’ odds to see overround/juice as a percentage. Prefer sharper markets (lower hold) when shopping prices; investigate negative hold as a possible arbitrage.

Use it to turn a prediction-market contract price in cents (for example 65¢ ≈ 65%) into American, decimal, and fractional sportsbook-style odds so you can compare venues on the same scale.

Use it when buying or selling half a point on a spread or total and you want an estimate of how much the fair price should move — especially around key numbers where half a point is more valuable.

Use it to translate a point spread into estimated moneylines from historical league relationships. It is a general equivalence tool, not a game-specific forecast.

Use it for count-based props when you have an expected average rate (λ) and want the chance of exactly, at least, or at most k occurrences — for example goals, hits, or similar counting markets under a Poisson assumption.

Profit is only what you win on top of your stake. Total payout is profit plus your original stake returned if the bet wins. A $100 bet at +300 earns $300 profit and $400 total payout.