How to Read American Odds: What +150 and -110 Actually Mean

Open any sportsbook and you’ll see numbers like +150 or -110 next to a bet. Those are American odds, and once you know how to read them, every other number on the page — parlay payouts, implied probability, the vig — starts to make sense. This is the language the rest of this blog assumes you speak, so it’s worth ten minutes now.

Plus and minus: two sides of the same coin

American odds always describe a bet relative to $100.

• A minus number (like -110 or -200) tells you how much you’d need to risk to win $100. At -110, you risk $110 to win $100. At -200, you risk $200 to win $100. The bigger the minus number, the more “favored” that outcome is considered — and the less it pays relative to your stake.
• A plus number (like +150 or +300) tells you how much you’d win if you risk $100. At +150, a $100 bet wins $150. At +300, a $100 bet wins $300. The bigger the plus number, the more of an underdog that outcome is considered.

You don’t have to bet exactly $100 — the ratio just scales. A $55 bet at -110 wins $50; a $20 bet at +150 wins $30.

Converting odds to implied probability

Every price also encodes an implied probability — the win rate the odds suggest, before you even ask whether that’s a good number. The formulas:

• Minus odds: probability = odds ÷ (odds + 100)
• Plus odds: probability = 100 ÷ (odds + 100)

Using illustrative round numbers, not a posted line: -110 works out to 110 ÷ 210 ≈ 52.4%. A price of +150 works out to 100 ÷ 250 = 40%. Notice the minus price implies a higher chance of winning — that’s the whole point of the sign. Favorites (minus) are priced to win more often; underdogs (plus) are priced to win less often but pay more when they do.

You don’t need to run this math by hand every time — the parlay calculator will convert and combine odds for you automatically.

Why two -110 prices don’t add up to 100%

Here’s the detail that trips people up: if you convert both sides of a two-way market — say, a moneyline or an over/under both priced at -110 — the implied probabilities don’t sum to 100%. They sum to a little more, something like 104–105%.

That extra few percent isn’t a rounding error. It’s the vig (short for “vigorish,” also called the juice) — the built-in margin a sportsbook bakes into both sides of a market. It’s how the book gets paid regardless of the outcome, and it’s the reason implied probability from the odds is always a little higher than the true probability of the outcome. We break vig down in detail in a separate post, but the shorthand is: the further the total implied probability sits above 100%, the more margin is baked into that price.

Why this matters once legs start stacking

A single -110 bet is easy to eyeball. But once you combine legs into a parlay, the odds — and the vig on each leg — compound. A small edge lost to juice on one leg becomes a bigger drag once it’s multiplied across three or four legs on the same ticket. Reading American odds fluently is step one; seeing how they interact once they’re stacked together is step two.

That second step is exactly what the Bettorly parlay analyzer is built to show — it takes the odds format you now know how to read and shows you what happens when several of them are combined on one ticket.