Tools
Prop break-even calculator
Type in both sides of a player prop and see what the price actually says: the implied probability of each side, how much vig the book is charging, and the no-vig fair line. Add your own estimate and it prices your edge in dollars.
Common prop prices at a glance
Every price is a probability wearing a costume. This reference table converts the prices you will actually see at the counter into the win rate you need just to break even — before any vig adjustment.
| American odds | Implied probability | Break-even win rate | $100 stake wins |
|---|---|---|---|
| -150 | 60.00% | 60.00% | $66.67 |
| -135 | 57.45% | 57.45% | $74.07 |
| -120 | 54.55% | 54.55% | $83.33 |
| -115 | 53.49% | 53.49% | $86.96 |
| -110 | 52.38% | 52.38% | $90.91 |
| -105 | 51.22% | 51.22% | $95.24 |
| +100 | 50.00% | 50.00% | $100.00 |
| +105 | 48.78% | 48.78% | $105.00 |
| +110 | 47.62% | 47.62% | $110.00 |
| +120 | 45.45% | 45.45% | $120.00 |
| +150 | 40.00% | 40.00% | $150.00 |
How to read a prop price
A negative American price tells you how much you must risk to win $100; a positive price tells you how much $100 of risk wins. Hidden inside either format is a probability. At -115, you risk $115 to win $100, which only makes sense if the outcome hits at least 115 ÷ 215 =53.49% of the time. That number is both the implied probability and your break-even win rate — they are the same thing said two ways.
The catch is that a two-way prop market quotes both sides above their true probability. That is the vig, and it is why comparing your projection to a single posted price flatters the bet.
Worked example: Over -115 / Under -105
Take a receiving-yards prop posted at Over -115 / Under -105:
- Implied over: 115 ÷ 215 = 53.49%
- Implied under: 105 ÷ 205 = 51.22%
- Market total: 53.49% + 51.22% = 104.71% — a 4.71-point overround
- No-vig over: 53.49 ÷ 104.71 = 51.08%. Once the juice is stripped, the market thinks the over is barely better than a coin flip.
Now suppose your usage-based projection says the over hits 55% of the time. Your edge over the fair line is 55.00 − 51.08 = about 3.9 points. In dollars: a $100 stake at -115 pays $86.96 when it wins, so EV = 0.55 × $86.96 − 0.45 × $100 = +$2.83 per $100 staked. Real, but thin — which is the honest shape of most prop edges.
Why the no-vig line matters
The posted price is an offer; the no-vig line is the market's opinion. If you only compare your projection to the posted implied probability, you will "beat" plenty of lines that the market actually agrees with you on — the gap was just juice. Stripping the vig gives you the fair benchmark, and your edge has to clear it by enough to cover model error too. That discipline is the core of the process we lay out in player props through a usage lens.
The other half of the job is generating a probability worth trusting. Ours start from opportunity: snap share, route participation, target share and red-zone usage — the coaching decisions that repeat week to week. Browse the full player props desk for how those inputs become a number you can put against a line.
FAQ
What is implied probability in a player prop?
Implied probability is the win rate baked into a price. For negative American odds it is |odds| divided by (|odds| + 100), so -115 implies 115 / 215 = 53.49%. For positive odds it is 100 divided by (odds + 100), so +120 implies 100 / 220 = 45.45%. It is also your break-even win rate at that price.
What is the vig on a prop bet?
Add the implied probabilities of both sides of the market. A fair market would sum to exactly 100%; the excess is the vig, or overround. Over -115 / Under -105 sums to 104.71%, so the book is holding about 4.7 points of margin on that line.
What is a no-vig (fair) line?
The no-vig line removes the bookmaker margin by normalizing each side by the market total. With Over -115 / Under -105, the over is 53.49 / 104.71 = 51.08%. That 51.08% is the market’s actual opinion of the over once you strip the juice, and it is the number your own projection has to beat.
How do I calculate expected value on a prop?
EV per $100 staked = p × payout − (1 − p) × 100, where p is your estimated probability and payout is what $100 wins at the posted price: 100 × 100 / |odds| for negative odds, or the odds themselves for positive odds. At -115 with p = 55%, EV = 0.55 × $86.96 − 0.45 × $100 = +$2.83 per $100.
Why does a small edge over the posted line not mean a good bet?
Because the posted line includes the vig. Beating the implied probability of -115 (53.49%) is not enough if the no-vig market says 51.08% — your projection has to clear the fair line by enough to cover the juice and your own estimation error. Most disciplined bettors want several points of edge over the no-vig number before betting.
18+ / 21+ depending on your state. Analysis and opinion — not betting advice, and never a guarantee.