When someone asks, “What is the line on the Bears?” the question really is asking what the wager terms are to bet that the Bears will win, considering the spread. The “considering the spread” part is just understood.

The format will vary a little from sport to sport, but the essential elements remain the same. The football games might look something like the following, the Browns-at-Bears might look like this:

The numbers to the right are used for placing a bet on that team. The first team in the pair is the visiting team, and the second team is the home team. For games on neutral turf, if one team is designated home team for game purposes, it will be on the bottom row.

The larger of the two numbers to the immediate right of the team names is the total points expected in the game. The lesser of the two numbers is the point spread. The minus sign might be omitted to save space. Obviously, the absolute value of the spread will always be less than or (rarely) equal to the total. This sports book appears to believe that the odds on the two teams would be about even if we handicapped the Bears by a touchdown. It also seems to think that the total number of points to be scored in the game will not exceed 40.

A bet "for the Bears" would be a wager that they would win by more than seven points. In other words, the wager is against the spread. If the Bears succeed in exceeding the spread, they are said to have "covered the spread" - a good thing for those with action on the Bears. A bet for the Browns would win if the Browns either won the game or lost by fewer than seven points. (In that event, the Bears "did not cover".)

A tie in the bet, i.e., a Bears victory by exactly seven points, will usually result in a return of the bets. Nobody wins. The terms of the bet may dictate what happens in case of a tie, particularly in sports, like hockey and soccer, where ties are more common. The usual way to resolve this in the sports book is to make the spread a fraction of a point, thus ensuring no ties. A spread of 7.5 points would resolve ties in favor of the underdog. A spread of 6.5 would cause the favorite to win in a one-touchdown game. Sometimes the one-half point is not written out, but just indicated with an apostrophe after the point spread number. This is a "hook." Hooks sometimes are subtle, so be sure whether there is one or not before calculating a bet. This is especially true in a situation like football, in which the difference between 7 and 7½ points is a whole additional score of some kind.

In some books it is possible to "buy a half point" on NFL games, if you want to, which means to make a bet that would win also in the event of a tie. (Sometimes it is said that you are "buying the push.") The usual cost is to move the line from -110 to -120 (referred to as "costing ten cents"). The implicit shift in probabilities between -110 and -120 is the difference between 52.4% and 54.5%, or a 4% reduction in edge. (This is not a subtraction, the difference between the two is 2.1 percentage points, which is itself 4% of 52.4%.) If a push (or a tie) appears more than 4% of the time, then buying half a point would be worth doing. The frequency of ties will depend on the final spread of a game. In football, it should be intuitively obvious that outcomes with final spreads of three and seven are probably the most likely, given that points are mainly accumulated in multiples of three and seven. Outcomes with spreads of, say, six and fourteen might also be relatively common for the same reason. A final spread of four or five would be more unusual. Historical research confirms that intuition. It is worth buying half a point when the probability of a tie is more than 4½ or 5%, and that does occur when the spread is 3, 7, 14 and 17. Historically spreads of 10 and 6 are close, but not quite there. It is not worth doing for spreads of the more unusual numbers.

Now, returning to the "board," at the far right is the money line, which sometimes appears in football. Mainly it is the way betting is accomplished on games with relatively low scoring (like baseball) where point spreads would have less meaning and be imprecise. The money line is the pay off for a straight up bet with no spread. For example, a bet on the Bears to win would require $180 in order to win $100, and the bet would win if the Bears won the game outright, with no consideration of the spread. The plus sign indicates the bet is on the underdog. In this case, a bet of $100 would render $160 in winnings.

Finally, the main number is the large, -115 on the Bears and the +105 on the Browns. These numbers disclose the financial terms of the bet. Some people refer to this as the "point line" in a football wager, reflecting the fact that a certain number of points is taken away as a handicap. To win the proposition related to the Bears (that they win by more than 7 points), it will be necessary to risk $115 for every $100 in winnings. The bet can be any amount, but the ratio of bet to winnings will remain the same. Likewise, a bet of $100 on the Browns will net a winning of $105. This is potentially dicey, so it is worth reiterating: To bet the Bears, it takes $115 in a wager for the chance to win $100. To bet the Browns, it takes $100 in a wager for the chance to with $105. Note the difference in the amounts to be bet and the prize money offered.

Why, one might ask, are the terms for the favorite calculated differently from the terms for the underdog? The favorite's number is the amount you have to bet to win $100, and the underdog's number is the amount you win if you bet $100. Why is that, and isn't that confusing? Well, yes, it is confusing at first, but the system permits a certain consistency in thinking that comes in handy once the idea settles in. A negative number always reveals a favorite. The higher the number, the more favored it is. An 80% chance of winning would be portrayed as -400 (4:1 in favor). To win $100 requires betting $400, as the odds of taking home money are so high. Now the real bet could be just $20 for example. In such a case the favorite would generate $5 in profit.

A positive number always reveals an underdog. The higher the number, the more of an underdog it is. A mere 20% chance of winning would be portrayed as +400 (1:4 against). To win $400 would require betting $100. The real bet could be $20, and would generate $80 in profit, sixteen times as much as the same amount bet on the favorite.

The symmetry of the system is shown that the person who wagers on the favorite risks money in order to win just a little, but with a high chance of success. The person who favors the dog risks money in order to win quite a lot, but with a small chance of success. The financial expectations, over the long run, are the same.

The symmetry is also shown by the fact that with "balanced action" there will be enough money in the pool from all bettors to pay off the winners (with something for the casino, besides). If the supporters of the underdog prevail, the individual payoffs will be high, but to a few people. If the supporters of the favorite should win, the individual payoffs will be low, but there will be many more payees. Such is the underlying logic of favorites, underdogs and betting odds.

Another question often arises in connection with the terms (including a spread) if a money line is also given: Does an arbitrage opportunity exist? The answer is no, it is not really arbitrage, but there may be a scenario where the probabilities of winning by the spread are qualitatively different from winning without the spread, making one proposition more attractive than the other, depending on how one's handicapping has turned out. However, the wagerer should be aware that the research and analysis by the line setter that was devoted to calculating the terms of the spread also went into setting the numbers for the head-to-head outcome (sometimes called "straight up.")

An apparent inconsistency may be informative about what the line setter was thinking. In the example above, the money line gives a preference on the Bears side of 64.3%. (Spelling it out: -180 means a bet of $180 will yield $280 if it wins. The expectation implicit in this payoff is 0.643. This means the expected value of a $280 payoff on a $180 ticket implicitly assumes a 64.3% chance of success. The chance of success times the value of the outcome is cost of the ticket.) The opposite side of the money line, +160, shows an expectation of 38.5% that the Browns will win. These numbers do not add to 100, nor do they need to, but they should be somewhat close. (The chance of a tie is not considered.) Many things cause some discrepancies in the two sides of a single proposition. For example, it is possible that the original lines were somewhat closer to a balance, but the public's clear preference for the Bears, say, caused the house to move the line upwards (against) that team in an effort to balance the action, or perhaps take a little safe risk on its own part.

Now the -115 bet at a seven point spread presumes that the Bears have only a 53.5% chance of beating the spread, i.e., winning by more than seven points. The +105 bet on the Browns presumes a 48.8% chance that the Browns will prevail, i.e., not lose by more than six points. (Remember, the spread itself is a tie in this example.)

It is perfectly coherent that the odds of a win can be 64% or so, but the odds of a win by more than a touchdown turn out to be significantly lower. This depends on the history of the teams, and many other handicapping considerations. Likewise, history might show that although the underdog only has a 38% chance of winning outright, the odds are almost even that it will hang on to be within a touchdown of the winner.

It may be helpful to think of the spread bets as an attempt by the sports book to bring the two teams into some kind of balance. So the -115 bet is a kind of fulcrum designed to balance the action. The spread is made large enough against the favorite to attract balanced action, that is, public support in roughly equal amounts for each side. As a result, the handicapped outcomes will hover in the 50% area, whereas the non-handicapped results can be (and often are) very lopsided.

The spread does not necessarily imply the house's prediction of the outcome (though it can). It is often just a prediction of where the public will go in the betting. Thus, opportunities for the sharp wagerer persist, in part because the sports book is trying to catch balanced action, even if the terms give up some ground to the informed gambler.

Notice also that the + (plus) number is never higher in absolute value than the -- (minus) number. If this were any different, then the sports book could lose money on balanced action. The mechanics are reasonably simple: Assume balanced action on the betting proposition used in the example above. Take the simplest case of one money line bet per side. The $100 on the Browns goes to the book, with the prospect of a $260 payout. The $180 on the Bears goes to the book with the prospect of a $280 payout. Either way, the book now has $280 in cash and a liability of either $280 or $260, depending on the outcome. If the "real" odds are about 50-50 on the proposition, the book has an expectation, over the long run, of netting $10 (half the time making $20 and half the time breaking even). The book may set its props so that the favorite, as handicapped, wins somewhat less often than the dog. Then the expected profit would be higher. In any event, the number on the underdog can not be higher than the number on the favorite, or else the book has created "negative space" in which to operate financially.

The terms on the favorite are normally -110. The Bears/Browns example used slightly different terms just for illustration, as the -110 number is often omitted altogether, with the understanding that the absence of explicit terms in a point line implies -110. So if there is no -115 or -170 or whatever, the terms are the "standard" -110.

A good many props at -110 on the point line for the favorite will offer even money ("EV") on the underdog. This creates a $10 space for the house. Sometimes the odds with the spread will move slightly to make a minor adjustment, up to -115 or -120, as in the example above. In the Browns at Bears, it was evidently felt that the one touchdown spread was just slightly generous to the favorite, so the line moved a little to make up for it.

Sometimes, if the house feels it can do so, the gap between the favorite and the dog can be more than $10 -- perhaps as high as $20. There is a limit to how hard the house can push on this interval between the two sides, as the action will flow towards the one that seems more advantageous, throwing things out of balance. However, if for some reason there is a lot of betting on one side for sentimental reasons (for example, on the Clippers because a lot of LA gamblers go to Vegas, drink hard and become optimistic), the house may set the line so as to harvest that money, without necessarily resetting the other side of the prop. This would, of course, create edges for sharper players, and should be pounced upon.

This "space" between the two sides of the wagers is regarded as the house "vig." On the standard -110/even proposition, it turns out to be $10 out of $210 of action ($110 from the favorite's side and $100 on the dog). Either way, the payout to a winner is $100, leaving $10 for the book to compensate it for its trouble in running the bet. If $1 out of every $21 bet stays with the house (as a minimum, when the house does not engage in any risk taking of its own), the vig comes to 4.8%.

Now it is true that the winner receives the payoff without deduction of any fee, but there is still a vig in there somewhere. If the house could work for free, the $10 leakage from the betting pool would not take place, and the betting terms would be closer to the "real" odds.

The lesson is that if the -110/even scenario is really trying to establish a balance around 50-50, the implicit expectation in the -110 bet is 52.4% -- above the 50% mark by exactly half the vig of 4.8%. Positive edges of less than 2.4% are losing propositions because of the vig. This is what is meant by "transactions costs" in betting. The edge has to be more than just break even in order to justify play, because the cost of the transaction itself must be paid out of the funds in the transaction.

In summary, then, the "normal" betting terms are against the spread in the case of betting on a favorite, or within the spread, if betting on the dog. In some cases, there will be no spread, but rather, a money line, showing the terms for a bet on the outcome of the contest "straight up" with no spread. Occasionally there will be both. Many experienced sports bettors refer to these bets as "straight bets," to distinguish them from the exotics, parlays, teasers, etc.

It may be useful, as a starting proposition, to make a table of percentages based on the terms of sports wagers. Then, when you confront terms like -270, you can readily determine what probability of outcome this number implies. This will help evaluate an offered line, since the handicapping of sporting events often winds up as a percentage figure. This can then be compared to the percentage implicit in the terms of the prop.

The following figure shows how to make this table. In a spreadsheet program, after putting in the column headings, put in the formulae as indicated and copy down as many rows as desired to complete the picture. Note that at 50% the formula changes. In Las Vegas the term "-100" does not exist, although it certainly could. It would be identical to "+100." But it is called "even" or just "EV." The calculation for the positive numbers is different from the minus numbers because of the shift of focus from amount of wager to amount of reward. Enter the percentages as decimal fractions and then format them to show up as percentages, if you like.