ODDSFLOOR

Free no-vig calculator, plus Kelly, hold, arbitrage, parlay and a converter

Short answer: six betting calculators that run the same formulas as the OddsFloor board, in the open. Paste two prices and get the fair line under six devig methods. Enter a bankroll and an edge and get a Kelly stake. No account needed for the calculators.

Open the calculators

The six

• No-vig fair odds. Two prices in, the margin out, the fair line under six methods (multiplicative, additive, power, Shin and worst-case among them) shown side by side.
• Arbitrage. Two prices at two books. Tells you if they cross, the return, and how to split the stake. The live arb finder uses the same formula.
• Kelly stake. Edge, price, bankroll and the fraction of Kelly you want. Out comes the stake.
• Hold. How much margin a book is taking on a market, so you can tell a 2% book from a 7% one.
• Parlay. Fair parlay price from the fair legs, next to the price the book offers, so the correlation and the stacked margin are visible.
• Odds converter. American, decimal, fractional and implied probability, both ways.

Why the methods disagree, and why that matters

On a coin flip every devig method lands in the same place. On a longshot they split, because books don't spread their margin evenly. They load it on the side the public likes. Multiplicative devig pretends they don't. Power and Shin try to account for it. The calculator shows all six so you can see how much of a "fair" number is the method, not the market.

This is the same reason the +EV board prints the method it used on every row. An edge that only exists under one devig method is a weak edge.

What they don't do

• They don't tell you a bet is good. A fair line is only as good as the prices you feed it. Feed it two soft books and you get a soft fair line.
• They don't know the market's close. For that, log the bet in the tracker.
• They don't replace the board. The board does this across 55+ books at once, and only for books you can bet at.

FAQ

What does a no-vig calculator do?

It takes a book's two-sided quote, which adds up to more than 100%, and solves the margin out so each side's implied probability is what the book really thinks. That's the fair price. Compare any book's offer with it and you can see who's giving you the better number.

Why six devig methods?

Because they disagree, and the disagreement is information. Multiplicative, additive, power, Shin and the others agree on a coin flip and split on longshots, where the margin is loaded unevenly. The calculator shows them side by side so you can see how much a fair number depends on the method.

Which Kelly fraction should I use?

Full Kelly assumes your edge estimate is exact. It never is. Most people who size by Kelly use a quarter to a half of it, which gives up a little growth for a lot less variance. The calculator takes the fraction as an input and shows the stake for the bankroll you enter.

Are these the same formulas the board uses?

Yes. The calculators and the +EV board share one math library. A fair number you work out by hand on the calculator is the fair number the board prints on its row.

More: how OddsFloor compares with the paid screeners · about OddsFloor