MLB Baseball Betting–The Math Behind Moneyline Underdogs


In the previous two articles we talked about the danger of betting big moneyline favorites and then introduced a couple of concepts to explain why baseball moneyline underdogs are so attractive to a serious bettor. We’ll continue our discussion of MLB underdog betting by adding the quantitative component. In other words, we’ll do the math.

It’s fairly simple so try to follow along—the best place to begin is with the MLB baseball standings. Any standings will do—the full year standings from 2015, the current 2016 standings, whatever. What’s important is the winning percentage of each team. Notice that on balance even the best teams lose 40% of their games and the worst teams win 40% of their games. There are a few exceptions here and there but not many. The Chicago Cubs are winning games at a 71% clip so far in 2016 but they’re getting dealt prices that make profitability tough even with that percentage.

In 2015, only two teams finished with a winning percentage of over 60% and they didn’t do it by much—the St. Louis Cardinals won 61.7% of their games and the Pittsburgh Pirates won 60.5% of their games. Likewise, only two teams finished with a winning percentage of under 40% and once again not by much. The Philadelphia Phillies won 38.9% of their games and the Cincinnati Reds won 39.5% of their games.


Keep that 40% to 60% range in mind and we’ll look at some betting lines. Once again, we just need some for the purpose of explaining these concepts. I’m using the lines from the Don Best screen on June 7, 2016. All betting lines have ‘implied probability’ or to look at it another way a ‘theoretical breakeven point’. For flat bets in pointspread sports you’ll usually lay -110 on either side making the implied probability (or theoretical breakeven) 52.38%. It’s common knowledge that you have to hit 53% or above to make money in pointspread sports laying -110 and the ‘theoretical breakeven’ explains why.

So let’s plug in some of our ‘average baseball win percentage’ numbers. 60% implied probability (which we get from our ‘average best win percentage’ in MLB baseball) translates to a money line of right at -150 (-149.99 to be exact). From a theoretical standpoint, this means that you should be very cautious when laying more than this price in baseball. There might be situations where it is justified but if you find yourself doing this often you should probably re-evaluate your handicapping process.

Now the flip side and why serious baseball bettors love underdogs. Lets look at that 40% winning percentage and factor out the implied probability there. At 40% implied probability we get a moneyline of +150. In very broad terms, this means that if you’re betting all but the worst teams at a price over +150 you’re getting an overlay!
And don’t forget that the 40% to 60% range represents the extremes in most years. Look again at the standings and notice how many teams are grinding along just above 50% winners. If you have an implied probability of over 50% and you’re betting an underdog you’re getting line value by definition. This is because 50% implied probability translates to a +100 moneyline.

Again, this is a very simplistic explanation just to illustrate how easy it is to put the math in your favor when betting baseball underdogs. We’ll expand on these theoretical concepts—on both sides of the ‘plus/minus sign’–in future articles. In the meantime, it’s a good idea to track down an odds converter calculator. You can do this with any calculator but there are plenty of specialized ones just for odds conversion online. You can also get odds converter calculator apps for your Android or Apple iOS phone. When you start thinking of betting propositions and prices in these terms you’re entering the world of a ‘sharp’ sports bettor.