Sports Betting Calculators
Four free in-browser calculators every serious bettor needs: parlay payouts, sportsbook hold percentage, no-vig fair odds, and Kelly criterion bet sizing. No signup, no server-side data, work offline once loaded.
Pick a Calculator
Odds Converter
Convert any line between American, Decimal, and Fractional formats and see the implied probability. Includes a conversion cheat-sheet for the most common odds.
Open →Parlay Calculator
Calculate the payout of any parlay across any number of legs. Switch between American, decimal, and fractional odds inline.
Open →Hold Calculator
Given a two-way market, compute the sportsbook's hold percentage (theoretical edge). Find the sharpest pricing on a given market across books.
Open →No-Vig Odds Converter
Strip the sportsbook vig from any two-way market to see the implied "fair" odds. Useful for line-shopping and value-bet identification.
Open →Kelly Criterion Calculator
Compute the optimal bet size based on your edge and bankroll using the Kelly criterion. Includes fractional Kelly preset for risk-controlled bettors.
Open →Expected Value (EV) Calculator
Enter your probability estimate and offered American odds to compute expected value per dollar staked, edge percentage, and Kelly stake recommendation.
Open →Hedge Calculator
Lock in profit on a bet that has appreciated. Enter your original bet + opposing line; get the hedge stake that equalizes payouts and your guaranteed profit floor.
Open →Arbitrage Calculator
Surebet finder. Detect 2-way arbitrage opportunities across operators and compute the optimal stake distribution that locks in guaranteed profit either way.
Open →Bonus Value Calculator
Convert sportsbook welcome offers to actual cash-equivalent value after rollover, minimum-odds restrictions, and time constraints. Compare offers honestly.
Open →Frequently Asked
Are these calculators free to use?
Yes. All four tools run entirely in your browser, with no signup, no tracking, and no server-side computation. They work offline once the page loads.
Why is bet sizing important?
Even bettors who pick winners consistently can go broke if they bet too large relative to their bankroll. The Kelly criterion gives the mathematically optimal bet size; in practice most bettors use fractional Kelly (typically half-Kelly) to reduce variance.
What is "vig" or "juice"?
Vig (vigorish) or juice is the sportsbook's built-in margin on a market. A two-way market priced -110 / -110 has roughly 4.5% vig; meaning the implied probabilities sum to 104.5% rather than 100%. Tighter pricing (lower vig) means better long-term value for the bettor.
How do I calculate a parlay payout manually?
Convert each leg to decimal odds, multiply them together, then convert the product back to your preferred format (or just multiply by your stake to see the payout). The parlay calculator does this automatically and shows the work.