Free Betting Tools
Calculators and simulators for arbitrage bettors, value bettors, and prediction market traders. No signup, no ads.
Arbitrage Calculator
Calculate arb %, optimal stake split, and guaranteed profit for 2-way and 3-way sure bets. Decimal, American, and fractional formats supported.
Arbitrage & Value Bet Calculator (In-Depth Guide)
Middle bet finder, Asian handicap mode, no-vig value detection, and a full written walk-through of arbitrage math for prediction markets and sportsbooks.
No-Vig Calculator (Devig / True Odds / Fair Odds)
Strip the bookmaker margin from any 2-way or 3-way market to compute true probabilities and fair odds. Decimal, American, fractional input/output. Proportional, Shin, and Logarithmic methods.
Kalshi Fair Odds Calculator
Devig Pinnacle or PS3838 prices to find the fair cents price for any Kalshi contract. Proportional, Shin, and Logarithmic methods with Kalshi fee adjustment.
Prediction Market EV Calculator
+EV math for Kalshi and Polymarket binary contracts. Price in cents, probability in percent, real Kalshi fees and Polymarket gas baked in with quarter-Kelly sizing.
Bankroll Growth Simulator
Monte Carlo simulator with animated growth curves. See how your edge compounds over hundreds of bets, compare flat vs Kelly staking, and visualize risk of ruin.
Odds Converter
Instantly convert between decimal, American, fractional, and implied probability formats. Single and bulk conversion modes with copy-to-clipboard.
Expected Value (EV) Calculator
Calculate the expected value of any bet. Enter odds and true probability to find your edge, break-even win rate, and EV per dollar. Includes a Closing Line Value (CLV) mode.
Kelly Criterion Calculator
Find the mathematically optimal bet size. Enter odds, win probability, and bankroll to get full, half, and quarter Kelly stakes with expected growth rate.
Hedge Bet Calculator
Calculate the exact hedge stake to lock in guaranteed profit on any open bet. Includes a free bet / bonus bet hedging mode with conversion rate tracking.
Matched Betting Calculator
Calculate lay stakes, qualifying losses, and free bet profits. Extract maximum value from bookmaker bonuses with the back/lay method.
Parlay & SGP Calculator
Build parlays, generate round robins, and find hidden edge in correlated same-game parlays. The only free parlay calculator with a correlation-aware SGP mode.
Bookmaker Hold & Margin Calculator
See exactly how much juice your bookmaker charges. Compare margins across books and find the sharpest prices. Detects arbs when best-line hold goes negative.
Dutching Calculator
Split your stake across multiple selections for equal profit no matter which wins. Dynamic leg builder with up to 20 selections and visual stake allocation.
Prediction Market Profit Calculator
Calculate real profit on Kalshi and Polymarket after all fees. Includes Kalshi fee tier breakdown, Polymarket gas costs, and a cross-venue arbitrage mode that shows guaranteed profit.
Free Tools for Smarter Betting
Whether you're an arbitrage bettor looking for sure bets across sportsbooks, a value bettor hunting for +EV edges, or a prediction market trader working Kalshi and Polymarket, the right calculators make the difference between guessing and knowing.
Every tool on this page is free, instant, and runs entirely in your browser. No signup, no data collection, no limits. Just enter your numbers and get results.
Who Are These Tools For?
- Arbitrage bettors: Use the arb calculator to verify opportunities, the odds converter to compare across formats, and the hedge calculator to lock in profit
- Value bettors: Use the EV calculator to find +EV bets, the Kelly criterion calculator for optimal stake sizing, and the bankroll simulator to plan your growth
- Prediction market traders: Use the prediction market calculator to understand Kalshi fees and Polymarket gas costs, and find cross-venue arbitrage opportunities
Why Free Betting Calculators Matter
Most bettors lose money because they rely on gut feeling instead of math. A sports arbitrage opportunity only exists when the numbers prove it. A value bet only has positive expected value when the probability math checks out. These tools let you verify every decision before risking real money.
For serious bettors who want to automate the entire process (detection, calculation, and execution), Claw Arbs runs these calculations across thousands of markets simultaneously, placing orders in milliseconds when edges appear.
Frequently asked questions
Which calculator should I use to find arbitrage bets?
For 2-way and 3-way sure bets, use the Arbitrage Calculator above. To strip the bookmaker margin from odds, the No-Vig Calculator computes true probabilities. For a walk-through of the full workflow (identify, verify, stake split), read our arbitrage betting calculator guide.
Are these betting calculators actually free?
Yes. Every calculator on this page is free, runs entirely in your browser, and requires no signup or account. There are no ads, no data collection, and no usage limits. Bookmark this page and use the tools as often as you like.
What's the difference between value betting and arbitrage betting tools?
Arbitrage tools (like the Arbitrage Calculator and Hedge Calculator) help you lock in a guaranteed profit across two or more bets on the same event. Value betting tools (like the EV Calculator and No-Vig Calculator) help you find single bets with positive expected value. Both approaches can be profitable but carry different risk profiles. Read Value Betting vs Arbitrage for the full comparison.
Can I use these calculators on Kalshi and Polymarket?
Yes. The Prediction Market Profit Calculator is purpose-built for Kalshi and Polymarket, with Kalshi fee tiers and Polymarket gas costs baked in. The Kalshi Fair Odds Calculator and Prediction Market EV Calculator both handle cents-based prediction market prices natively.
How accurate are the calculator results?
The underlying math is deterministic and matches the industry-standard formulas used by professional bettors. Where fees, gas costs, or slippage matter (Kalshi, Polymarket, some crypto sportsbooks), those are baked into the relevant calculators. Just be aware that odds can move between the moment you calculate and the moment you place a bet, so always verify the current price at the venue.
Which calculator do I need if I'm just starting out?
Start with the Odds Converter to get comfortable with decimal, American, fractional, and implied probability formats. Then use the EV Calculator to understand expected value and the Kelly Criterion Calculator to size bets. When you're ready to arb, jump to the Arbitrage Calculator. For a full primer, read our what is sports arbitrage betting guide.