Betting 101
How Odds Actually Work
4 min read
TL;DR
American odds are just probabilities wearing a costume. -150 means the book thinks it hits about 60% of the time. Learn the conversion and every line on every board becomes readable.
Odds are prices, not predictions
A line like -150 or +200 isn't the book telling you who wins. It's a price — what you pay for a chance at a payout. Negative numbers show how much you must risk to win $100; positive numbers show how much you win on a $100 stake.
- -150 → risk $150 to win $100
- +200 → risk $100 to win $200
The conversion that unlocks everything
Every price implies a probability:
- Negative odds: implied % = odds ÷ (odds + 100). So -150 → 150/250 = 60%
- Positive odds: implied % = 100 ÷ (odds + 100). So +200 → 100/300 = 33%
Once you think in percentages, you can compare any line to what you believe the true chance is. That gap — your estimate vs. the book's — is the entire game. Everything else on this site (hit rates, EV badges, model picks) exists to help you estimate that true chance better.
Try it on a real board
Open Prop Picks and pick any line. A -140 Over implies 58.3%. Now look at the player's L10 hit rate next to it. Higher than 58%? Interesting. Lower? You're paying more than the recent record justifies. That one habit — convert, then compare — is the foundation for every other lesson here.
Keep these
- Odds are prices that imply probabilities — always convert
- -150 = 60% implied, +200 = 33% implied
- Compare implied probability to your best estimate of the true chance
Up next
What +EV Really Means