On the eve of the NFL season (or at least most of the games) lets talk about teasers. NFL teasers are a very powerful weapon when used correctly, but sportsbooks keep them as a betting option due to the fact that many people do not use the properly.
First, lets break down what a teaser really is. A teaser is just a parlay with a great marketing name. When laying -110 on a wager, you must win that wager 52.4% of the time in order to break even. When that wager has more than one leg, you need to determine the needed winning percentage of each leg. In the instance of a two team teaser, each leg must win 72.4% of the time. You calculate this by multiplying 72.4 by .724 which comes out to 52.4.
If it is assumed that a standard side wager will win 50% of the time, this means that the 6 points you move the spread must increase the win percentage of each leg by at least 22.4% (72.4-50). If you were to tease every game this season, you would change the outcome of around 15-16% of each game. This falls well short of the 22.4% needed and a majority of your teaser wagers would be losers. Your sweet spot covers what is known as "Wong teasers". These occur when you move a 1.5, 2 or 2.5 point dog, or a 7.5, 8, or 8.5 point favorite. By teasing teams with these totals, you are moving through the 3 and the 7. This has a history of changing outcomes 24-25% of the time, but we'll use 24% to be conservative.
So if using Wong teasers causes the win rate for each leg to jump to 74%, we use the same multiplication as we previously used.
74 x (.74) = 54.76.
So out of 100 games, 54.76 times you would win one unit. 45.24 times you would lose 1.1 unit for a total of +5 units. A standard two team wong teaser at -110 has 5% equity.
But unlike parlays, where your return gets worse as you add legs, a teaser is actually the opposite.
It is important to use books with the best teaser lines. Betmania is still the only book I know of that offers even money two teamers, but there are several that offer great odds for teasers with multiple legs.
3 team (+180)-Betmania, Legends, Payouts plus group (Betpop, Youwager), Diamond
4 team (+300)-Betmania, Legends, Payouts plus group (Betpop, Youwager), Diamond
6 team (+700)-Betmania, Legends, Payouts plus group (Betpop, Youwager), Justbet
Here is a list of win rates for each wong teaser, along with their equity based on the above payouts:
3 team: 40.5%. 13.4%
4 team: 30%. 19.9%
6 team: 16.4%. 31.3%
Although betting more teams creates greater EV, it also significantly increases your volatility. That must be taken into account when choosing which route to go when betting teasers.
Although there sample size is not large, I would not recommend teasing 7.5-8.5 road favorites as they have not done as well as all other categories.