Prop bets, short for proposition bets, are bets on something that happens inside a game rather than on the final result: a player's points, a striker's shots on target, the number of corners. Bet builders, sold as same game parlays (SGPs) in the US, let you combine several of those markets from one match into a single bet.
Both are now among the most heavily promoted products on sportsbook apps, and the reasons mostly favour the sportsbook. Props carry wider margins than the main lines, and combining them from one game adds a pricing problem that only the book can see inside. Our parlay and accumulator guide covers the basics of how bet builders are priced. This article goes further: how prop lines are set and settled, why their margins run higher, how correlation decides the fair price of a combination, and where props can still be worth a look.
Player props, team props and game props
Sportsbooks group props in roughly three ways, although the labels vary from one app to another.
Player props are tied to one player's statistics. In the NBA that means points, rebounds, assists and three-pointers made. In the NFL it means passing, rushing and receiving yards, receptions and touchdowns. In football (soccer) the usual markets are anytime goalscorer, shots, shots on target, tackles, fouls and 'to be shown a card'. In cricket, a batter's runs or a bowler's wickets.
Team props cover one side's numbers: team points, team goals, corners or cards. Game props cover the whole match without being the main result, such as first team to score, total corners in the match, or whether there will be a penalty.
Most player props come in one of two formats. The first is an over/under line, such as a guard's points at over or under 24.5, priced close to even money on both sides. The second is a ladder of milestone or alternative lines, such as 20+, 25+ and 30+ points, each priced separately and usually offered on the 'yes' side only. That difference matters as soon as you try to work out the margin.
Why prop margins run higher than main lines
On a main NFL or NBA point spread the standard price is -110 on both sides. Each side implies 52.38%, a total of 104.76%, so the overround is 4.76%. Many player props are priced at -115 on both sides instead, which is about 1.87 in decimal. That implies 53.49% each and 106.98% in total, an overround of about 7%. Some prop lines sit at -120 on both sides, a total of 109.09%. The jump from 4.76% to 7% looks small, but it is roughly half as much again as the margin on the spread.
One-sided markets are harder to check. If a sportsbook offers a player to score 30+ points at +220 (3.20) and nothing on the other side, you cannot add two prices together to see the margin. The +220 implies 31.25%, and that figure includes a margin you cannot measure. A $10 bet at that price wins $22. The same applies to anytime goalscorer markets, where only a 'yes' price is shown for each player. Judging these needs an estimate of your own or a comparison across several books. Our guide to implied probability shows the conversions.
Books charge more on props for practical reasons. They price hundreds of props per match, each with less data behind it than the match result. A player's output depends on expected minutes, which can change with a late injury or a tactical switch. And fewer bettors compare prop prices across sportsbooks, so competition is weaker. Sportsbooks also tend to set lower maximum stakes on props than on main lines, which tells you they know these prices are easier to get wrong.
How props are settled
Prop settlement is where many disputes start, so read the rules for each sport before you bet. Common principles, with the caveat that each sportsbook writes its own:
- Participation: a player prop is usually void if the player takes no part. In football, many books void an anytime goalscorer bet on a player who never comes on, but let it stand if he appears as a substitute, however late. US books differ on how much a player has to play for a prop to stand.
- Official data: props are settled on the statistics provider the sportsbook uses, which can differ from a broadcast graphic, especially for shots on target, tackles and assists.
- Own goals: goalscorer markets do not count them.
- Time period: football props normally cover 90 minutes plus stoppage time only. In the NBA and NFL, overtime usually counts for player props, but check the market rules.
- Cards: books differ on whether cards shown to substitutes on the bench or after the final whistle count.
Bet builders add another layer. If one player in a bet builder does not play, some sportsbooks remove that leg and settle the rest at a lower price, while others void the whole bet. Check which rule applies before you add a player whose fitness is in doubt.
Correlation: what a bet builder should really pay
An ordinary acca multiplies prices from separate events, which only makes sense if the results are independent. In a bet builder the legs come from the same match, so they are linked, and the fair price of the combination depends on how strongly.
Take a home team at 1.90 to win and its main striker at 2.30 to score anytime. Multiplied together, that is 4.37. Now suppose your own estimates are a home win at 50% and the striker scoring at 40%, and that when the home team wins the striker scores 60% of the time. That implies he scores 20% of the time when they do not win, which keeps his overall figure at 40%. The chance of both happening is 50% × 60% = 30%, so the fair price of the pair is 1 ÷ 0.30 = 3.33. If the legs really were independent it would be 1 ÷ (0.50 × 0.40) = 5.00.
This is why sportsbooks cannot simply multiply bet builder legs: on positively linked combinations they would pay far too much. They run a model that estimates the joint chance and quote a price from that. Suppose the bet builder offers 3.00 for the pair. On your numbers that pays 90% of the fair 3.33, an expected loss of 10% per bet, because 0.30 × 3.00 - 1 = -0.10. The two singles at their own prices are cheaper: the home win at 1.90 has an expected loss of 5% (0.50 × 1.90 - 1) and the striker at 2.30 an expected loss of 8% (0.40 × 2.30 - 1). The combination costs more than either leg on its own.
Correlation can also run the other way. Legs that rarely happen together, such as a 0-0 draw and a named player having three or more shots on target, have a joint chance below the simple product, so the fair price is higher than multiplying suggests. The narrow opportunity some bettors look for is a positive link the model underrates, so that the combined price is too generous. Sportsbooks update these models constantly, cap stakes on bet builders and block combinations they consider too closely linked, such as a team to win to nil alongside the opponent to score.
Same game parlays in US sports
A typical NBA same game parlay might combine a team on the moneyline at -150 (1.667), its leading scorer over 24.5 points at -115 (1.870) and its centre over 10.5 rebounds at -115. Multiplied as if independent, those prices give 1.667 × 1.870 × 1.870 = 5.83, or about +483 in American odds. The sportsbook will usually quote less, because a team that wins is more likely to have had a big night from its best scorer, and the rebounds leg is linked to both.
Even before any correlation adjustment, the margin stacks. Three legs each carrying an overround of about 7% pay roughly 1 ÷ 1.07 to the power of three = 82% of the fair combined odds. With main-line pricing at 4.76% per leg the same calculation gives about 87%. Every extra leg pushes the figure lower. For more on the main NBA markets see our guide on how to bet on the NBA, and for NFL player props see how to bet on the NFL.
Promotions such as boosted same game parlays change the arithmetic on that one bet, but they are usually capped at small stakes, and the price being boosted may already carry a large margin. Work out what the boosted price implies before assuming it is generous.
Where props can still be worth a look
Props are not hopeless. The things that make them hard to price for the sportsbook, many markets, noisy data and fast-changing information, are the same things that occasionally leave a price behind. Bettors who do find value in props tend to find it in a few places:
- Team news and minutes. A prop line is built on expected playing time. When a starter is ruled out late, the players who absorb his minutes may have lines that have not caught up.
- Narrow specialist knowledge, such as which full-back takes the corners or which midfielder commits the most fouls, where the book's model may be generic.
- Price comparison. Prop lines vary more between sportsbooks than main lines do, so the same player can carry different lines at different books on the same day.
- Matchups and style, such as pace of play in basketball or a side that concedes a high number of shots from distance.
The limits are real. Books cap prop stakes and often restrict accounts that win on them steadily, and any edge has to be proven by records rather than by a good week. Our guide to value betting explains how to test your own estimates against closing prices.
Pricing a bet builder before you place it
Here is the full routine on a football bet builder: home win, over 2.5 goals and the home striker to have at least one shot on target, offered at 3.50.
Start with your own estimates for the first leg and then each leg given the ones before it. Say the home win is 55%. Given a home win, you rate over 2.5 goals at 60%. Given a home win with three or more goals, you rate the striker's shot on target at 78%. The joint chance is 0.55 × 0.60 × 0.78 = 25.7%, a fair price of 3.89. To break even at 3.50 you need the joint chance to be at least 1 ÷ 3.50 = 28.6%, so on these numbers the bet has an expected loss of about 10% (0.257 × 3.50 - 1 = -0.099). If you had treated the legs as independent, using overall estimates of 55%, 52% and 65%, you would have put the fair price at 5.38 and badly overstated what the sportsbook was charging. Most of the gap between 5.38 and 3.50 is correlation; the part that remains, about 10%, is margin.
Before you place a prop or bet builder:
- Check the line and price at more than one sportsbook.
- Convert both sides to implied probability where both are shown, and add them to see the margin.
- Confirm the player is expected to play and read how the book settles a non-runner in a bet builder.
- Estimate the joint chance yourself, allowing for correlation, rather than trusting the combined price.
- Stake a three or four-leg bet builder as the long shot it is.
Betting laws differ by country and, in the US and India, by state, so check the rules where you live and use a licensed operator. Props and bet builders are fast, repeatable bets during a match; if that starts to feel hard to stop, see our responsible gambling page.
Frequently asked questions
What is a prop bet?
A prop bet is a bet on an event within a game rather than its final result, such as a player's points, a striker's shots on target or the number of corners. Player, team and game props are the main groups.
Is a bet builder the same as a same game parlay?
Yes. Bet builder is the usual name in the UK and many other markets, and same game parlay is the US term. Both combine several selections from one match into one bet that needs every leg to win.
Why does a bet builder pay less than the legs multiplied together?
The legs come from one match and are often linked, so the chance of all of them happening is higher than the simple product suggests. The sportsbook prices that link in, and usually adds a margin on top.
What happens if a player in my bet builder does not play?
It depends on the sportsbook. Some remove that leg and settle the rest at a reduced price, while others void the whole bet builder. The rules are in the sportsbook's settlement terms, so check them before betting.
Are prop bets easier to win than main markets?
Not as a rule. Props usually carry a bigger margin than main lines. Some bettors find occasional value through team news or specialist knowledge, but stakes on props are often capped and winning accounts can be restricted.