Betting 101 · 4 min read

Understanding Betting Odds: American, Decimal, and Implied Probability

American Odds Explained

American odds are the standard format at US sportsbooks. They come in two flavors:

Negative Odds (-110, -200, -350)

The number tells you how much you need to bet to win $100.

**-110**: Bet $110 to win $100 (plus your $110 back)

**-200**: Bet $200 to win $100

**-350**: Bet $350 to win $100

Positive Odds (+150, +250, +500)

The number tells you how much you win on a $100 bet.

**+150**: Bet $100 to win $150

**+250**: Bet $100 to win $250

**+500**: Bet $100 to win $500

Converting to Implied Probability

Implied probability tells you what the odds say about a team's chances of winning:

**Negative odds**: probability = |odds| / (|odds| + 100)

- -150 = 150 / 250 = 60%

- -200 = 200 / 300 = 66.7%

**Positive odds**: probability = 100 / (odds + 100)

- +150 = 100 / 250 = 40%

- +200 = 100 / 300 = 33.3%

The Vig (Juice)

Notice that if you add up the implied probabilities of both sides of a bet, they total more than 100%. That extra percentage is the sportsbook's margin — the "vig" or "juice."

For a typical -110/-110 line:

Side A: 52.4%

Side B: 52.4%

Total: 104.8%

That 4.8% is the house edge. It's how sportsbooks make money regardless of the outcome.

Finding Value

A bet has "value" when your estimated probability of winning exceeds the implied probability from the odds.

If you think a team has a 55% chance of winning but the odds imply 50% (+100), that's a value bet. Over hundreds of bets, consistently finding these edges is how profitable bettors win.

Why This Matters for Tracking

When you track your bets with actual odds recorded, you can calculate whether you're finding value or not. SlipTrack captures the odds from your bet slips automatically and shows you implied probability alongside live win percentages during games — so you can see if the market agrees with your bet in real time.