Bad Math in Back Alleys: Why Sports Betting Odds are So Convoluted
The story of why you must risk $110 to win $100—and how bookies accidentally shortchanged themselves
By JV Miller
jv@professionalgambler.org
Sports betting has gone from back-alley whispers to prime-time commercials faster than you can say "Prop Bet." What was literally a federal crime for most Americans just a decade ago is now plastered across every sports broadcast. But if you've ever stared at betting odds and wondered why they look like they were designed by someone having a math panic attack, well—you're on the right track.
Why do you risk $110 to win $100? Why do Europeans call the same bet "1.91" while Americans slap a minus sign in front and call it "-110"? And why couldn't these people just use nice, round numbers like normal humans?
The answer lies in the murky origins of sports betting, back when placing a wager meant meeting some guy named Sal behind Tony's Liquor Store.
When Bookies Ruled the Shadows
Picture this: It's 1960-something, smartphones are science fiction, and pocket calculators won't exist for another decade. Sports betting is illegal everywhere, which means every bet happens in the shadows—literally. Smoky bars, back alleys, and hushed conversations were the norm.
Every neighborhood had "a guy"—the local bookie who took bets and somehow kept track of everything in his head or on scraps of paper. These weren't criminal masterminds running sophisticated operations. They were regular folks trying to make a living while staying one step ahead of the law.
Since meeting up to exchange money was risky business (you know, being illegal and all), bookies needed a system that was dead simple. No complex math, no lengthy calculations—just something any schmuck could figure out in his head while nervously glancing over his shoulder.
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The "Brilliant" Solution That Wasn't
So our entrepreneurial bookies came up with what seemed like pure genius: "eleven-to-win-ten." Bet $11, win $10. The extra dollar goes to the bookie as commission. Easy math, right?
"That's exactly 10% commission," they thought, probably feeling pretty clever about their mathematical prowess.
There was just one tiny problem: they were wrong.
The Accidental Discount
Here's where it gets embarrassing for our back-alley mathematicians. To charge a true 10% commission, they should have made bettors risk $10 to win $9. Instead, by making them risk $11 to win $10, they were actually charging just 9.1%.
Think about it: if you risk $11 and win $10, the bookie's $1 cut represents 1/11th of your total risk, not 1/10th. That's roughly 9.1%, not 10%.
Oops.
For decades, bookies across America were accidentally giving their customers a discount.
From Alleys to Apps
As sports betting evolved and eventually went legitimate, that flawed "eleven-to-win-ten" system got scaled up to "110-to-win-100," which morphed into today's "-110" odds that you see everywhere.
Meanwhile, Europeans developed their own system, expressing the same concept as decimal odds—hence "1.91" (you get $1.91 back for every $1 wagered, including your original stake).
Same bet, different notation, all stemming from bookies in smoky bars who couldn't quite nail the math.
The Irony of It All
What's truly hilarious is that this whole mess started because bookies wanted to keep things simple. No complicated calculations, no confusing fractions—just nice, clean mental math that anyone could handle.
Instead, they created a system so convoluted that modern bettors need calculators, conversion charts, and dedicated apps just to figure out their potential payouts. Sports betting apps now spend millions on user interfaces trying to make sense of a numbering system that was supposed to be simple enough for a guy named Sal to calculate in his head while chain-smoking behind a liquor store.
The next time you're staring at "-110" odds wondering why sports betting couldn't just use normal numbers, remember: it all started with some well-meaning bookies who thought they were simplifying the whole thing.
They weren't.
Good luck!
About the Author:
JV Miller is widely regarded as one of the world’s top professional sports bettors and handicappers. JV is a frequent expert contributor on national television and has penned op-eds for prestigious publications such as USA Today. A second-generation sports bettor, JV Miller is the son of J.R. Miller, the legendary sports bettor and author who wrote the best-selling book How Professional Gamblers Beat the Pro Football Point Spread.
The Miller family’s roots in sports betting trace back to the 1970s when they arrived in Las Vegas as industry trailblazers. This website was launched in 1997 and is the first sports handicapping website in history. As publisher of Professional Gambler Newsletter, JV is trusted by more professional and high-stakes sports betting clients than any other handicapping service worldwide.