There is a significant misunderstanding of how gambling odds at sportsbooks work. Whether it’s a new sports bettor who’s just learning, a casual bettor in the sportsbook, or the gambling bros on Twitter, it won’t take long to hear it.
“Why would you bet those odds!?”
The best example of this comes from the Mayweather/McGregor fight.
The event pinned an unbeaten boxer against a UFC juggernaut who had never boxed professionally in his life.
Recently, David Purdam of ESPN tweeted about how he bet Mayweather -1600. Purdam asked, “Did I make a bad bet?” and boy were the drones after him.
How on earth could Purdam, a gambling writer, bet a -1600 line!?
That’s irresponsible! Harrumph!
Actually, it’s pretty simple.
The -1600 odds imply a probability of winning at 94%. In hindsight, Purdam got a bad number–but the gambling world didn’t foresee the amount of McGregor money coming that would ultimately bring the number down to -400.
To this day, my largest bet I have ever made was on Mayweather.
Betting Probabilities
Out of all the responses Purdam got to his tweet, there was one response that stuck out.
“If that was the prevailing line and Mayweather was truly 94% to win, that bet is fine,” responded @AdamBStein.
Bingo.
The problem I see a lot within sports betting, especially from newer bettors, is they don’t understand the correlation between probability and odds.
Instead, people bet a +200 because they want the 2/1 payout–they don’t realize they are betting on a team that the sportsbook deems has a 33.33% chance to win.
When I started to bet based on probability, it created a monumental shift in how I approach everything. I started taking risks on bets that I felt were off.
The Correlation of American Odds to Implied Probability
Sports betting is part art and part science. It is vital to understand and know the math–particularly with the odds you are betting.
Learning the math in sports betting is the easy part. Memorize the chart below, bookmark it on your phone, use it in the sportsbook. Make sure you’re getting the right probability.
When I memorized this chart, I saw a massive increase in my winning during in-game betting. I guarantee, learning this chart will only improve your handicapping.
| Odds | Implied Probability | Odds | Implied Probability |
| -110 | 52.38% | +110 | 47.62% |
| -120 | 54.55% | +120 | 45.45% |
| -130 | 56.52% | +130 | 43.48% |
| -140 | 58.33% | +140 | 41.67% |
| -150 | 60.00% | +150 | 40.00% |
| -160 | 61.54% | +160 | 38.46% |
| -180 | 64.29% | +180 | 35.71% |
| -200 | 66.67% | +200 | 33.33% |
| -220 | 68.75% | +220 | 31.25% |
| -240 | 70.59% | +240 | 29.41% |
| -260 | 72.22% | +260 | 27.78% |
| -280 | 73.68% | +280 | 26.32% |
| -300 | 75.00% | +300 | 25.00% |
| -400 | 80.00% | +400 | 20.00% |
| -500 | 83.33% | +500 | 16.67% |
| -600 | 85.71% | +600 | 14.29% |
| -700 | 87.50% | +700 | 12.50% |
| -800 | 88.89% | +800 | 11.11% |
| -900 | 90.00% | +900 | 10.00% |
| -1000 | 90.91% | +1000 | 9.09% |
Convert American Odds to Implied Probability
There are two math formulas to convert American odds to their respective implied probability. For favorites with negative odds, you multiply the negative odds by -1 then divide that by the American odds plus 100, multiply by 100 to return a percentage.
( Negative Odds * -1 ) / ( Negative Odds + 100 )
The formula for underdogs is slightly different. Start with 100 divided by the Positive Odds and add 100, multiply by 100 to return a percentage.
100 / Positive Odds + 100
Final Thoughts
Everyone approaches handicapping differently–it’s a dynamic experience. Learning these formulas will improve your handicapping. But the nuance and art of betting are how you will win more.
These implied probabilities will vary from book to book. They don’t include the vigorish, either. So keep in mind, that you may find a book that shades these numbers slightly differently.
