Free betting calculators
Fast, no-signup tools for shopping prices and sizing bets. Everything runs in your browser — no accounts, no tracking, no fees.
- American · Decimal · Fractional · Probability Odds Converter Convert any betting price between American, decimal, fractional, and implied probability — and see the payout on your stake. Updates live as you type. Open tool →
- Combined odds, payout & round-robin Parlay Calculator Add 2–15 legs to get your combined odds, true win probability, and payout. Switch on round-robin to see every smaller parlay combination. Open tool →
- Remove the juice, find fair odds Vig & Hold Calculator Enter both sides of a market to reveal the sportsbook’s vig and hold, the no-vig fair odds for each side, and your edge at the listed price. Open tool →
- Lock in profit on either outcome Hedge Calculator Enter your original bet and the price on the opposite outcome to get the optimal hedge stake, your guaranteed profit, and the payout whichever side wins. Open tool →
- Expected value, edge & Kelly stake EV Calculator Enter the odds and your estimated true probability to see expected value per dollar, your edge over the line, and the recommended Kelly stake — colour-coded +EV or -EV. Open tool →
- Optimal & fractional bet sizing Kelly Criterion Calculator Enter your bankroll, the odds, and your win probability to get the full Kelly stake plus quarter, half, and three-quarter Kelly — with the math shown step by step. Open tool →
- Sure bets across two books Arbitrage Calculator Enter the two-way price from each sportsbook and your total stake to see if a sure bet exists, the stake on each side, and your guaranteed profit and ROI. Open tool →
- Equal profit on any winner Dutching Calculator Back 2–6 selections in one market and we split your total stake so the profit is identical whichever one wins — with the optimal stake and return on each. Open tool →
- Convert a free bet to guaranteed cash Free Bet Calculator Enter your free bet amount and the odds to see its true cash value, then lay or hedge the same selection to lock in a guaranteed profit whatever the result. Open tool →
- Cents ↔ American, decimal & probability Prediction Market Converter Turn a Kalshi or Polymarket price in cents (or 0–1.00 probability) into American, decimal, and fractional odds — and convert any sportsbook price back to a contract price. Open tool →
Comparison tools
Polymarket · Kalshi · PredictIt · Manifold Prediction Market Price Comparison The same question priced across every platform, side-by-side. See the cheapest price, the cross-platform spread, and where to back each side — the OddsChecker for prediction markets. Compare prices →Analyzers & finders
- Six questions · your top 3 books Sportsbook Finder Quiz Answer six quick questions and get your top three sportsbook matches — filtered by your state and ranked on the odds, app, bonuses, and features you care about. Open tool →
- Bet now or wait? Bet Timing Analyzer A “bet now or wait” tool inspired by flight-price predictors. Pick a matchup and bet type to see whether the odds are at their best or likely to improve. Open tool →
- Line-open to kickoff charts Odds Movement Tracker Watch how odds move from open to kickoff across DraftKings, FanDuel, BetMGM, and Caesars, with annotated injury and sharp-money points marking the best time to bet. Open tool →
Built for line shoppers
OddsGrab is a comparison engine, and these calculators exist to make comparing prices effortless. Convert an unfamiliar format, work out what a parlay actually pays, or strip the vig out of a line to see the fair number underneath — then use the best price you find across our sportsbook and prediction-market comparisons.
Put the calculators to work
These tools do the math behind real strategies. Our matched betting guide walks through using the odds converter and hedge calculator to extract near-guaranteed value from sportsbook sign-up bonuses, and the arbitrage betting guide shows where the arbitrage calculator finds sure bets across books.
For informational purposes only. Not betting or financial advice. Please gamble responsibly. 21+ where applicable.