The math is not the product. Here it is, free.
No-vig fair odds with multiplicative or Shin devig, an arbitrage stake split, and fractional Kelly sizing — computed entirely in this browser. No account, no log, nothing you enter leaves the page.
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Every price carries the book's margin. At -110 / -110 each side implies 52.38%, and the 4.76% above 100% is the hold — the cut you pay to bet. Fair probability divides the margin back out. Multiplicative removes it in proportion to each price; the Shin method assumes the book shades the favorite against insider money, so the favorite keeps more of the margin and the longshot gives more back. Fair odds are the no-margin price — the number a closing line is measured against. Same game, two honest answers; Shin is the one the engine uses.
When the combined implied probability of every side comes in under 100%, the shortfall is the margin and the stake split below pays the same amount no matter which side wins. When it is over 100%, no split exists and none is shown. An arb on screen is not money in hand: lines move between the first bet and the last, books limit accounts that take these prices, and void rules differ on retirements and pushes. The number is exact; the execution is not.
Kelly is the stake fraction that maximizes long-run growth when your probability is right — and it assumes your probability is right, which is the fragile part. Take the fair probability from the no-vig calculator above, not from a feeling. Full Kelly is a growth-rate answer, not a comfort answer: even with a real edge, a losing run at full Kelly will cut a bankroll in half sooner or later. A fraction gives up little growth for much smaller swings, which is why the engine sizes at a fraction and caps exposure. No edge, no bet — the calculator says so.
The scanner does this math across every book, every 5 minutes.
Every price the engine ingests is devigged with the Shin method, checked against every other book for a locked margin, and sized with fractional Kelly — on a 5-minute freshness clock, with stale prices flagged rather than hidden. A verified account starts a 14-day full-access trial for every qualified EV and arbitrage detail — no card. Calculators remain open without an account; membership keeps the full boards open after the trial.