Player props feel like the same bet as a side or total, but the price you pay is quietly worse. The reason is the overround: the sum of both sides' implied probabilities. On a standard side it sits near 105%; on a prop it is often higher, and that gap is the extra hold you never see on the slip.
A player prop — over or under on a passing-yards line, a points total, a strikeout count — looks like any other two-way market. You pick a side, you see a price, you place the bet. But props are, on average, one of the more expensive things on the board, and the reason is a single number that never appears on your bet slip: the overround.
What the overround is
Every price implies a probability. Convert both sides of a market to their implied probabilities and add them together, and in a fair world the sum would be exactly 100% — the two outcomes together are certain. Real markets always sum to more than 100%. That excess is the overround, and it is the sportsbook's margin expressed as a percentage.
Where a prop's extra cost comes from
Now price a prop the way books often do — say -120 on both the over and the under. Run the same arithmetic and the picture changes.
| -105 / -105 | overround 4.88% · hold 4.65% |
|---|---|
| -110 / -110 | overround 4.76% · hold 4.55% |
| -115 / -115 | overround 6.98% · hold 6.52% |
| -120 / -120 | overround 9.09% · hold 8.33% |
| -130 / -130 | overround 13.04% · hold 11.54% |
Why props are priced wider on purpose
The wider margin is not an accident, and it is not only greed. Props are genuinely harder and riskier for a sportsbook to price than a game side, and the margin is the book's compensation for that difficulty.
- Lower liquidity. Far less money flows through a single player's prop than through the game spread, so the book gets less price discovery from the market and leans on a wider cushion instead.
- Thinner information. A game total aggregates two full teams; a receiving-yards line depends on one player's usage, health, and game script, which are noisier to model.
- Correlation risk. Props inside one game are often linked, and bettors build them into same-game parlays. A wider single-prop margin is part of how the book protects itself against correlated action.
- Faster staleness. Props move on news — a scratched starter, a snap-count report — and a line that lags the news is exposed, so the book prices in a buffer.
What this does and does not tell you
- It does not say props are unbeatable. A bettor with a genuine edge on a specific player can overcome a wider margin — but the margin is a larger hurdle than on a standard side, so the edge has to be larger too.
- It does not price any specific prop for you. The example prices are illustrations of the arithmetic; the actual overround depends on the two real prices you are quoted.
- It is not a pick. This is how to read the cost of a prop, not a recommendation to take or fade one.
Frequently asked
What is the overround on a bet?
It is the sum of the implied probabilities of both sides of a market. A fair market sums to 100%; real markets sum higher, and the excess is the sportsbook's margin. A standard -110/-110 side sums to about 104.76%, so its overround is roughly 4.76%.
Why do player props have higher hold than the main lines?
Props are lower-liquidity, harder to model from limited information, more prone to correlation inside same-game parlays, and quicker to go stale on news. A wider margin compensates the book for all of that, which is why props priced -120 both ways carry roughly double the hold of a -110 side.
How do I calculate the hold from two prices myself?
Convert each price to implied probability, add them to get the overround, then divide the overround-above-100% share by the total. For -120/-120: each side is 54.55%, the sum is 109.09%, and the hold is 9.09% / 109.09% = 8.33%.
Is a higher overround always a worse bet?
It is always a higher cost to overcome, but whether a bet is 'worse' depends on your edge. A larger margin means you need a larger genuine advantage to profit. This article measures the cost; it does not tell you whether you have the edge to beat it.