Sports Betting Series - Point Spreads
For games between two teams, point spreads are designed to create a balanced bet on both sides of the matchup. Many games would not be beatable without it as the moneyline odds would be prohibitive to bet into. This type of wager helps to keep games competitive (even if in actuality the game has a heavy favorite) as it adds different betting opportunities to a one-sided matchup.
In terms of sports betting, point spreads have been one of the most useful inventions to encourage betting action and consequently is one of the most familiar types of sports wagers in the US.
Lets see how this works in action, here is an example from the NFL:
|Cardinals||(+4) -110||+170||O (49.5)|
|Rams||(-4) -110||-190||U (49.5)|
The point spread here shows the Los Angeles Rams as a 4-point favorite over the Arizona Cardinals. The minus before the four indicate the Rams are the favorites, the plus sign before the four indicate the Cardinals are the underdogs. If you would prefer to bet on the winner outright, you could get +170 on the underdogs, meaning if you spend $100 dollars on the moneyline (and win), you would get back $170 in winnings. Likewise if you spent $100 on the Rams to win outright at -190 odds, you would get about $53 back in winnings.
However if you would like more balanced odds, the spread is the best option. Let's say you really believe in the Rams as winners and concluded that they would win despite a -4 point handicap, you could bet the Rams on the spread with your $100, and take back $91 in winnings compared to the moneyline.
A line can move both in the moneyline odds and in the spread. Typically once a line reaches -115 in the spread, the next price move - assuming money comes in at those odds - will be a half-point or full point in the spread. For example, the Rams opened at -4 -110 in the spread and if money came in at those odds the next move would be -4.5 -110 on the point spread. Of course it is important to be aware that lines don’t always move in a predictable pattern.
Due to the high scoring nature of basketball and football - with a wider range of score outcomes unlike hockey, baseball or soccer - spreads on high-scoring sports will be more varied. Point spreads are less effective in lower scoring sports but they do exist. Usually these types of sports don’t use ‘points’, instead it is called the run line in baseball, handicaps in soccer and the puck line in hockey.
Covering the Spread
Covering the spread is another way to say a team won a points spread bet. Often experts and sports columnists will look at a teams history at covering the spread to see how well sports brokers have been at projecting a teams performance. You might also see the phrase, against the spread used, or its abbreviation ATS. The ATS record of a team is simply the wins and losses against the spread.
In certain cases where there is no favorite, a game will be listed as a pick’em, or its abbreviation PK. This means that there is no points spread, and all bets on the outcome are in effect moneyline bets.
Key Numbers & Buying the Half-Point
Football is unique among US sports in that the final margin of victory often lands on certain key numbers, as points in football tend to be scored in threes and sevens. It is easy to work out why games are frequently decided by three, seven, 10 or 14 points over for example, five, nine, 12 or 15 points. How is this quantified by sports brokers, and how do bettors make use of this information?
If bettors look for value across different sports brokers, the differences in half-points could be the edge required. For example, suppose you find two sportsbooks offering different point spreads on the same game. If they are both listed at the same price, e.g. +4 -110 and +4.5 -110 you will take the free extra point. But what happens if you have to pay more vig at one sportsbook for the extra half, e.g +4 +100 and +4.5 -110. Which line offers more value?
To compare different lines, bettors can use a push chart that estimates how many cents each half-point is
worth - i.e. a fair price on or off that number.
|Half - Point||NFL (in cents)|
Since we value buying off the 4 at 7 cents, +4.5 +100 offers slightly more value compared with +4.5 -110 (as the extra +0.5 in spread is being valued at 10c by the sportsbook), identifying any inefficiency between competing sportsbooks could lead to an edge over the market. This is called buying the half-point in football and most reputable sportsbooks will allow for this.
Spreads vs Moneyline
In our previous article I went over moneyline odds and how to interpret them, and it may seem that the point spread and moneyline are separate propositions, however the two betting options are intrinsically linked.
Comparing a point spread to moneyline is not quite the same as valuing an extra half-point in the push chart
above, but there is a predictable relationship between the two. Below is an approximate conversion chart
assuming there is no vig.
In our NFL example from the top of the page, the Cardinals are +4 -110 on the spread and +170 on the moneyline. Comparing it with the chart above you can see there is little value in betting the moneyline for the Cardinals, in fact you are effectively betting on the Cardinals as if they were +3.5 underdogs on the spread. Every tiny edge helps when comparing odds across sportsbooks and across betting lines to give you better bang for your buck.
The moneyline and spread should usually align as the chart above but that is not always the case. One of the most famous examples is the Super Bowl, where the public's preference for betting the moneyline often leads to pricing mismatches.
Both charts above are reverse engineered using far more complicated mathematics than is required to understand for the average bettor; I have repurposed both charts from James Holzhauer’s fantastic primer on sports betting at the Athletic and hope they serve as useful tools to understand sports betting in the US.