Betting Calculators

Odds converter

Change any one and the rest follow.

No-vig fair odds

Takes the book's margin (the vig) out of a market to get each side's fair chance, five ways. Use a sharp book's or an exchange's prices. Add your own price to see its EV.

• Multiplicative scales every side by the same amount. Simple, but it leaves longshots a little too likely.
• Additive takes the same amount off each side. It can't be used when a longshot's chance is smaller than its share of the vig.
• Power raises each chance to one power so they add up to 100%, taking more from longshots. A good default.
• Shin models a book pricing against sharp bettors. On two sides it matches additive.
• Worst-case is each side's lowest fair chance of the four: the cautious number to call a bet +EV.

Expected value

What a bet makes on average, given its true chance. Get the chance from the no-vig calculator above.

Kelly stake

How much of your bankroll a +EV bet is worth. Most bettors use a fraction of Kelly, since true chances are never known exactly.

Hedge & arbitrage

Hedge: what to bet on the other side of a bet you hold so you net the same either way. Arbitrage: how to split money across two books when both sides together pay more than they cost.

Bonus bet converter

A bonus bet only pays its winnings, not the stake. Bet it on a longshot and hedge the other side with your own money to lock in cash, usually 60–80% of the bonus. Find bonuses in the Bonus Finder.

Parlay

Every leg has to win. Put the legs' odds in one box, separated by commas or spaces. Add fair chances to see the parlay's EV.

Round robin

Every smaller parlay you can make from your legs, with the same stake on each, so one losing leg doesn't sink everything.

Poisson

For counts like goals, strikeouts, or shots: from the number you expect, the chance of going over or under a line. Add the book's prices to see their EV.

Spread ↔ moneyline

A spread's matching moneyline, and the other way round. Final margins are modeled as a bell curve around the spread: NFL's 13.86 points is the classic measure (Stern); the others are rough. Change it to suit.

Half point

Is buying half a point worth its price? It only matters when the game lands exactly on the number (3 in −3 → −2.5), so it comes down to how often that happens. Roughly 14–15% of NFL games are decided by exactly 3 and about 9% by 7; most other numbers far less, and basketball's spread evenly across many numbers.