How to use our betting & prediction market calculators

Odds Assist Pro includes a full library of free calculators at /calculators, split into two groups: calculators for traditional sports betting, and calculators for prediction markets like Kalshi, Polymarket, and Robinhood.

Every calculator on this page is free to use, no account required.

How they work

Each calculator takes a small set of inputs—odds, wager amount, fee structure, and so on depending on the tool—and instantly computes the output (payout, profit, ROI, fair odds, etc.) as you type. There's nothing to submit and nothing is saved; refreshing the page resets it.

Sports Betting Calculators

• Arbitrage Calculator – Calculate recommended bet sizes, payouts, profit, and ROI for your arbitrage bets.
• Closing Line Value Calculator – See what value you got on a bet and your estimated expected value.
• Betting Odds Converter – Convert between American, Decimal, Fractional, and Percentage odds formats instantly.
• Odds Payout Calculator – Calculate how much you'd win and profit based on bet amount and odds in any format.
• Free Bet Conversion Calculator – Convert free bets and bonus bets into guaranteed profit by finding the optimal hedge amount.
• Point Spread to Moneyline Calculator – Convert point spreads to moneyline odds for NFL, NBA, NCAAF, and NCAAB.
• Vig Calculator – Calculate the sportsbook vig on any betting market with unlimited outcomes.
• Kelly Criterion Calculator – Calculate optimal bet size using the Kelly Criterion for bankroll management.
• Round Robin Calculator – Calculate payouts and profit for round robin parlays with unlimited legs.
• Expected Value Calculator – Calculate the expected value (EV) of a bet to see if it has positive long-term value.
• Parlay Calculator – Calculate parlay odds and potential payout for multiple bets with unlimited legs.
• Teaser Calculator – Calculate the payout for an NFL or NBA teaser bet based on points teased and number of picks.
• Implied Probability Calculator – Calculate implied probability from betting odds in any format.
• Hedge Calculator – Calculate the optimal hedge bet amount to guarantee profit or minimize losses.
• No-Vig Odds Calculator – Remove the vig from betting lines to find true odds and implied probabilities.
• Profit Boost Calculator – Calculate how much extra profit a sportsbook profit boost token adds to your bet.
• Hold Calculator – Calculate a sportsbook's hold percentage—the expected revenue it keeps—from the odds on a market.
• Bankroll Calculator – Find your optimal betting unit size based on your bankroll and risk profile.
• Middle Calculator – Calculate the win-win window and worst-case outcome for a middle bet across two sportsbooks.
• Sports Betting Tax Calculator – Estimate the federal and state tax owed on your sports betting winnings and other gambling income.

Prediction Market Calculators

• Prediction Market to Odds Converter – Convert prediction market prices to betting odds, with equivalent American odds and implied probability.
• Prediction Market Payout Calculator – Calculate payout, profit, and ROI for Kalshi, OG.com, or Robinhood contracts with accurate platform fees.
• Kalshi Fee Calculator – Calculate the fees you'd pay when betting on Kalshi prediction markets.
• Kalshi Payout Calculator – Calculate your exact payout, profit, and ROI for Kalshi contracts, including maker and taker fees.
• Kalshi Odds Converter – Convert Kalshi contract prices to American, Decimal, and Fractional odds instantly.
• Kalshi Combo Calculator – Estimate the combined price and payout for a Kalshi Combo (a parlay-style multi-trade contract), assuming independent trades.
• Polymarket Fee Calculator – Calculate the fees you pay as a taker or the rebate you receive as a maker on Polymarket.
• Polymarket Payout Calculator – Calculate your exact payout, profit, and ROI for Polymarket contracts, including taker fees and maker rebates.
• Polymarket Odds Converter – Convert Polymarket contract prices to American, Decimal, and Fractional odds instantly.
• Polymarket Combo Calculator – Estimate the combined price and payout for a Polymarket Combo (a parlay-style multi-trade contract), assuming independent trades.
• Robinhood Fee Calculator – Calculate the fees you'd pay opening or closing event contract positions on Robinhood.
• Robinhood Payout Calculator – Calculate your exact payout, profit, and ROI for Robinhood event contracts, including Standard and Gold account fees.
• OG.com Fee Calculator – Calculate the fees you'd pay opening or closing positions on OG.com.
• DraftKings Predict Fee Calculator – Calculate fees for trading event contracts on DraftKings Predict.
• Crypto.com Fee Calculator – Calculate fees for trading prediction market event contracts on Crypto.com.
• FanDuel Predicts Fee Calculator – Calculate the 2% payout fee on a winning FanDuel Predicts prediction (no fee applies if you lose).
• Fanatics Markets Fee Calculator – Calculate fees for trading event contracts on Fanatics Markets.
• Underdog Predicts Fee Calculator – Calculate fees for trading event contracts on Underdog Predicts.