Why Understanding Odds Matters
Odds aren't just numbers — they represent probability, potential payout, and the bookmaker's built-in margin all at once. Before you place any bet, understanding what those numbers actually mean is the most fundamental skill you can develop. This guide covers the three most common bet types you'll encounter on any sportsbook.
The Three Main Odds Formats
Odds are displayed in different formats depending on where you're betting:
- American (Moneyline) odds: e.g. -150 or +130 — common in North America.
- Decimal odds: e.g. 1.67 or 2.30 — common in Europe and Australia.
- Fractional odds: e.g. 2/1 or 5/4 — traditional in the UK.
This guide focuses primarily on American odds since they're the format most online sportsbooks use globally, but the concepts apply to all formats.
Moneyline Bets
A moneyline bet is the simplest wager: you're picking who wins the game outright. The odds tell you how much you win or must risk.
| Odds | What It Means | Profit on $100 stake |
|---|---|---|
| +200 | Underdog — bet $100 to win $200 | $200 |
| -150 | Favourite — bet $150 to win $100 | $67 (on $100 stake) |
| +100 (even) | Pick'em — equal chance implied | $100 |
The minus sign always indicates the favourite (you risk more to win less). The plus sign indicates the underdog (you risk less to win more).
Point Spread Bets
Point spreads level the playing field between mismatched teams. The favourite "gives" points; the underdog "gets" points. You're not just picking a winner — you're picking a winner by a margin.
Example: Team A -6.5 vs. Team B +6.5
- If you bet Team A (-6.5), they must win by 7 or more for your bet to win.
- If you bet Team B (+6.5), they must either win outright OR lose by 6 or fewer points.
Spread bets are typically offered at -110 on both sides, meaning you risk $110 to win $100. That $10 gap is the bookmaker's commission (the "vig" or "juice").
Totals (Over/Under)
A totals bet has nothing to do with who wins — you're betting on the combined score of both teams. The sportsbook sets a line, and you bet whether the actual total will go over or under it.
Example: NBA total set at 218.5 points
- Over: The two teams must combine for 219 points or more.
- Under: The two teams must combine for 218 points or fewer.
Like spreads, totals are usually priced at -110 on each side.
What Is the "Vig" and Why Does It Matter?
The vig (vigorish) or juice is the bookmaker's built-in commission. When both sides of a bet are priced at -110, you're paying a small premium over a true 50/50 bet. Over time, this margin ensures the bookmaker profits regardless of outcomes.
To break even betting at -110, you need to win approximately 52.4% of your bets — not 50%. This is why disciplined bankroll management and selective betting are so important.
Converting Odds to Implied Probability
Every set of odds implies a win probability. Here's how to calculate it:
- For negative odds (e.g. -150): 150 ÷ (150 + 100) = 60% implied probability
- For positive odds (e.g. +130): 100 ÷ (130 + 100) = 43.5% implied probability
If you believe the true probability is higher than the implied probability, you may have found a value bet. Identifying value is ultimately what separates informed bettors from recreational ones.
Key Takeaways
- Minus odds = favourite; plus odds = underdog.
- Point spreads require you to win by a margin, not just outright.
- Totals are independent of the result — only the combined score matters.
- The vig means you must win more than 50% to be profitable.
- Always convert odds to implied probability to assess value.