What Do These Betting Odds Mean?

Many people use betting markets to shape their expectations.

James Tierney
4 min readNov 5, 2020


Baishampayan Ghose, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

I enjoy gambling. On sporting events, at the poker table, or an election. Heck, give me some odds on the number of claps this post will get, and I’ll make a bet.

In the betting world, the more likely event is called the favorite, whereas the less likely event is called the underdog. Over the past 36 hours, the betting markets for the next president of the United States have been all over the place. First favoring the challenger, Joe Biden, then favoring current President Donald Trump, before swinging back to having Biden heavily favored (which is where we stand as I finalize this post).

While it is important to know who is the favorite and who is the underdog in certain contests, how much of a favorite or underdog is just as important. That is where the betting odds come into play. The three most popular betting odds are American odds, fractional odds, and European (or decimal) odds.

American Odds

American odds are what I’m most familiar with as most US sportsbooks — the clearinghouse for legal sports betting in the US — use these types of odds.

When looking at American odds, you want to think about relating the presented number to a $100 bet. A plus (+) sign indicates the amount of money you would win from a $100 wager. A minus (-) sign indicates the amount of money you would need to wager to win $100.

For example, at the time of this writing, BetOnline.ag has the following betting lines for Joe Biden and Donald Trump:

Odds captured at 8:00 pm ET on November 4th, 2020

For Biden, since we see the minus (-) sign in front of the odds, you must risk $650 to win $100. Of course, you can do larger or smaller amounts, depending on limits. For example, you could risk $65 to win $10. Or $6,500 to win $1,000. But it’s easiest to think of the odds in terms of $100 amounts.

For Trump, since we see the plus (+) sign in front of the odds, you will get $500 for every $100 risked. Of course, you can…



James Tierney

Economics Educator. Improviser. Community Builder. Always looking for the next new thing, for better or for worse.