Player Prop Odds Calculator
A prop is worth betting only when your chance of it beats the chance its price implies. At -115 the over has to hit 53.5% of the time just to break even; the calculator takes the book's cut out of the over and under to show the fair odds, turns your projection into a chance, and says which side, if either, has the edge.
Prop odds, fair odds and your edge
Type the over and under prices. The calculator takes the book's cut out to show the fair odds, then weighs them against your own chance of the over, typed in or worked from a projection.
American (-115, +120) or decimal (1.87). Leave the under empty for a one-sided price.
Your chance of the over
Over
Under
EV is the average profit or loss a $100 bet over many bets like it, if your chance is right. Kelly is the share of a bankroll the Kelly criterion would bet; most bettors use a quarter of it or less.
The same player, stat and line at each book. Example prices are filled in; type what your books show.
| Book | Over | Under | Hold |
|---|
Locking in the gap
What does a prop price say about its chance?
Every price is a chance in disguise. Decimal odds are the easiest to read: a price of 1.87 says the bet has to win 1 in 1.87 times, 53.5%, to break even. American odds turn into the same thing. A minus price like -115 means risk $115 to win $100, so the break-even is 115 ÷ (115 + 100) = 53.5%. A plus price like +120 means risk $100 to win $120, so the break-even is 100 ÷ (100 + 120) = 45.5%.
Add the over's chance and the under's together and the total is always more than 100%. The extra is the book's margin, the vig or juice. The calculator reports it as the hold: the share of the money the book keeps if it takes the same amount on both sides, 1 − 1 ÷ (the two chances added).
| Over / under | Over implies | Under implies | Hold | Fair over |
|---|---|---|---|---|
| -105 / -105 | 51.22% | 51.22% | 2.38% | 50.00% |
| -110 / -110 | 52.38% | 52.38% | 4.55% | 50.00% |
| -115 / -105 | 53.49% | 51.22% | 4.50% | 51.08% |
| -120 / +100 | 54.55% | 50.00% | 4.35% | 52.17% |
| -130 / +110 | 56.52% | 47.62% | 3.98% | 54.27% |
| -140 / +115 | 58.33% | 46.51% | 4.62% | 55.64% |
| -150 / +125 | 60.00% | 44.44% | 4.26% | 57.45% |
How do you take the vig out of a prop?
Scale the two chances down so they add up to 100%. That is the no-vig, or fair, price: what the market thinks the chance is once the book's margin is gone. At -115 / -105 the over implies 53.49% and the under 51.22%, 104.71% together. The over's fair chance is 53.49 ÷ 104.71 = 51.08%, which is about -104 in American odds, and the under's is 48.92%, about +104.
This proportional method is the plainest way to do it and the one the calculator uses. Other methods spread the margin differently, putting more of it on the long shot; on a two-way prop priced near even they agree to within a fraction of a percent. A fair price from one book is only that book's opinion. The fair price from a book that takes big bets and moves its lines on them, or from the best prices across several books, is a better guide to the true chance, which is why sharp bettors check it before betting a softer book's line (how sharps bet NBA props).
How do you turn a projection into a chance?
A projection of 25.6 points against a line of 24.5 says the over is likely; it does not say how likely, and that is the number the price is weighed against. The answer depends on how much the stat swings from game to game, which is what the two models in the calculator are for.
- Normal, for points, yards and other stats with a wide range: it needs your projection and the standard deviation, how far a typical game lands from the average. Take it from the player's recent game log. With a projection of 25.6 and a standard deviation of 6.5, the chance of 25 or more points is 56.7%. At -115 that is worth +6.0% a bet.
- Poisson, for counts that come one at a time, like strikeouts, threes, sacks, or touchdowns: it needs only the average, because the spread of a Poisson count is fixed by its mean. A pitcher projected for 6.2 strikeouts gets to 6 or more 58.6% of the time. Over 5.5 at -130, with +110 on the under, is 54.3% once the vig is out, and at 58.6% it is worth +3.7%.
On a whole-number line, a total of 7 against a line of 7, the bet is a push and the stake comes back. The calculator works out that chance too and leaves it out of the win and the loss. A model is only as good as the projection behind it: minutes, role, the opponent and the game script move a player's numbers more than any formula, and real stats spread out more than a Poisson count does, so treat a small edge from a model with caution.
What is EV, and how much should you bet on an edge?
Expected value is what the bet makes or loses on average if your chance is right. At 56% on an over at -115, a $100 bet wins $86.96 56% of the time and loses $100 44% of the time: 0.56 × 86.96 − 0.44 × 100 = +$4.70, a 4.7% edge. The break-even is the price's own chance, so the edge is simply how far your number sits above it.
The Kelly criterion, from John Kelly's 1956 paper on information rates, is the stake that grows a bankroll fastest if your chances are exactly right: the edge divided by the profit a $1 bet would make. Your chances are never exactly right, and full Kelly swings hard, so most bettors stake a quarter or a half of it, or a flat 1% to 2% unit. The bet sizing calculator shows what each does to a bankroll over a season, and bankroll management, step by step sets the rules round it.
How much is shopping for the best line worth?
The same prop is often priced differently at different books, and the best price on each side is a smaller hold than any one book charges. The second panel finds the best over and under and the hold of the two together. Taking -105 instead of -115 lowers the break-even from 53.5% to 51.2%, so a bettor who wins 54% of the time goes from a 1.0% edge to a 5.4% one without picking any better. Where the best over and best under add up to less than 100%, the panel works out the two stakes that pay the same whichever side wins. Books do not leave those gaps open long, and they may limit an account that takes them every time. More in line shopping strategy explained.
Only compare the same line. An over 24.5 at -115 and an over 25.5 at +100 are different bets, and the calculator cannot tell how much the extra point is worth to you. For that, see how books price alternate lines, or run each line through the projection panel.
More on finding props worth betting: NFL betting strategy for prop bettors, NBA live betting strategy for props and the strategy Reddit's sharps actually use. To log every bet and see whether you beat the closing price, use the prop bet tracker.
Sources: the odds, implied chances, hold and fair prices are arithmetic on the prices typed in (the proportional method, as in the Action Network's How to Remove Juice/Vig from Sports Betting Odds); the normal and Poisson distributions as defined in the NIST/SEMATECH e-Handbook of Statistical Methods (normal, Poisson); the stake rule from J. L. Kelly Jr., "A New Interpretation of Information Rate", Bell System Technical Journal 35 (1956). The answers are only as good as the chance you give it; no calculator makes a bet a sure thing. Sports betting is for adults where it is legal in your state. If gambling stops being fun, call or text 1-800-MY-RESET.