Eight tools every sharp uses, free to anyone. No-vig fair odds, Kelly stake sizing, parlay math, EV, hedging — all the math, none of the gimmicks.
Why use it: Every sportsbook bakes a profit margin (the "vig" — typically 4-7%) into their odds. The true fair odds are hidden underneath. Devigging strips out the vig to show what a zero-edge book would offer.
How it helps: Compare your own win probability to the devigged fair probability. If your model says 56% but fair is 52%, you have a 4 percentage point edge — a positive-EV bet worth taking.
Example: Both sides at -110 → 52.4% / 52.4% implied, but fair is 50% / 50%. Book is taking ~4.8% hold.
Why use it: Stop guessing whether a bet is "good." EV (expected value) tells you exactly how much you should expect to win or lose per dollar wagered over the long run.
How it helps: If EV is positive, the bet is mathematically profitable in the long run. If negative, the book has the edge — pass.
Example: If you think a team has a 55% true win probability at -110 odds, EV on a $100 stake is +$4.76. You would average +$4.76 profit per identical bet over thousands of trials.
Why use it: The Kelly Criterion is the mathematically optimal bet size given your edge. Bet too small, you leave growth on the table. Bet too big, one bad streak ruins your bankroll.
How it helps: Type in your bankroll, your win probability, and the odds — get the exact dollar amount to wager for maximum long-run growth. We default to quarter-Kelly because full Kelly is too volatile in practice. Most pros use 1/4 to 1/2 Kelly to survive variance.
Example: 55% win prob at -110 odds with a $1000 bankroll → bet $24 at quarter-Kelly. Full Kelly would be $97 (10% of bankroll — too risky for most).
Why use it: Calculate the combined odds and payout when combining 2-12 bets into a single ticket. Helps you decide if a parlay payout justifies the lower hit rate vs straight bets.
How it helps: See exactly what you would win if all legs hit, and your implied probability of cashing the whole ticket. Most parlays are negative-EV because vig compounds across legs — this calc shows you the math clearly.
Example: Three -110 legs → +595 combined odds, $695 payout on a $100 stake. Implied probability of all hitting: ~12.5%.
Why use it: After a long-shot bet cashes (or the first leg of a big parlay hits), you can lock in locked profit by betting the opposite side. Removes outcome risk completely.
How it helps: Tells you exactly how much to wager on the hedge so you profit equally whether the original bet wins or loses. No more sweating the last leg.
Example: $100 at +500 wins → $600 payout if it cashes. Hedge with $240 at -150 on the opposite side → locked ~$260 profit either way.
Why use it: Find out how much "vig" or hold % the sportsbook is taking on a two-way market. Sharper books charge less, soft books charge more.
How it helps: Tells you which books to bet at. Low-hold books = closer to fair odds = better long-term value. High-hold books are taking more from you on every bet.
Example: -110 / -110 = 4.55% hold (mainstream). -105 / -105 = 2.38% hold (sharp). +100 / +100 = 0% hold (zero-vig promo — take it).
Why use it: Sportsbooks display odds in different formats — American (-110), decimal (1.91), fractional (10/11). Convert any format to a probability percentage to see what the book thinks the chances actually are.
How it helps: Compare the book implied probability to your own win probability instantly. If your model says higher than the implied, you have an edge worth pursuing.
Example: -110 → 52.4% implied. +200 → 33.3%. -200 → 66.7%. Type one format and the others auto-fill.
Why use it: Sportsbooks offer "risk-free" promos where if you lose, you get a refund as site credit (NOT cash). The true cash value depends on how much of that credit you can actually convert to cash.
How it helps: Calculate the actual cash value of any risk-free promo before claiming it. Higher odds + higher conversion rate = better value. Most pros assume ~70% credit-to-cash conversion.
Example: $500 risk-free bet at +100 odds with 70% conversion → +$175 expected cash value (35% of stake). Higher odds with the same conversion rate produces better EV.