What Are Betting Odds?
Betting odds represent two things simultaneously: the probability of an outcome occurring and the payout you'll receive if your bet wins. Every sportsbook—whether it's DraftKings, FanDuel, BetMGM, Caesars Sportsbook, or any other licensed operator—uses odds to communicate these two pieces of information.
Understanding how to read odds is the single most important foundational skill in sports betting. Without it, you can't evaluate whether a bet is worth placing, calculate your potential profit, or compare lines across different sportsbooks. This guide covers the three major odds formats: American, decimal, and fractional.
American Odds (Moneyline Odds)
American odds are the standard format used by sportsbooks in the United States. They're displayed as either a positive (+) or negative (−) number.
Negative American Odds (Favorites)
A negative number tells you how much you need to wager to win $100 in profit.
Example: The Kansas City Chiefs are listed at -150 to beat the Buffalo Bills.
- You must bet $150 to win $100 in profit.
- If you bet $150 and the Chiefs win, you receive $250 back ($150 stake + $100 profit).
Positive American Odds (Underdogs)
A positive number tells you how much profit you'll earn on a $100 wager.
Example: The Buffalo Bills are listed at +130 to beat the Kansas City Chiefs.
- A $100 bet returns $130 in profit if the Bills win.
- If you bet $100 and the Bills win, you receive $230 back ($100 stake + $130 profit).
Payout Formulas for American Odds
| Odds Type | Payout Formula | Example |
|---|---|---|
| Negative (−) | Profit = (Stake ÷ Odds) × 100 | $50 at -150 → ($50 ÷ 150) × 100 = $33.33 profit |
| Positive (+) | Profit = (Stake × Odds) ÷ 100 | $50 at +130 → ($50 × 130) ÷ 100 = $65.00 profit |
Decimal Odds
Decimal odds are the most widely used format globally, popular across Europe, Australia, and Canada. They're also the simplest to understand because the number directly represents your total return per dollar wagered (including your original stake).
Example: The Los Angeles Lakers are listed at 1.80 to beat the Boston Celtics, while the Celtics are at 2.10.
- A $100 bet on the Lakers at 1.80 returns $180 total ($100 stake + $80 profit).
- A $100 bet on the Celtics at 2.10 returns $210 total ($100 stake + $110 profit).
Payout Formula for Decimal Odds
Total Return = Stake × Decimal Odds
Profit = Stake × (Decimal Odds − 1)
| Bet | Stake | Decimal Odds | Total Return | Profit |
|---|---|---|---|---|
| Lakers ML | $75 | 1.80 | $135.00 | $60.00 |
| Celtics ML | $75 | 2.10 | $157.50 | $82.50 |
| Over 215.5 | $50 | 1.91 | $95.50 | $45.50 |
Decimal odds of 2.00 are equivalent to even money (American +100). Any decimal odds below 2.00 represent a favorite, and anything above 2.00 represents an underdog.
Fractional Odds
Fractional odds are the traditional format used in the United Kingdom and Ireland, particularly in horse racing. They're displayed as a fraction like 5/1 (read as "five to one") or 4/5 ("four to five").
The numerator (left number) represents profit, and the denominator (right number) represents the stake needed.
Example: A horse is listed at 7/2 to win the Kentucky Derby.
- For every $2 you wager, you win $7 in profit.
- A $100 bet returns $350 in profit plus your $100 stake back = $450 total.
Payout Formula for Fractional Odds
Profit = Stake × (Numerator ÷ Denominator)
Total Return = Stake × (Numerator ÷ Denominator) + Stake
| Fractional Odds | $100 Bet Profit | Total Return |
|---|---|---|
| 5/1 | $500 | $600 |
| 2/1 | $200 | $300 |
| 1/1 (evens) | $100 | $200 |
| 4/5 | $80 | $180 |
| 1/4 | $25 | $125 |
Implied Probability: The Hidden Number Behind Every Odds Line
Implied probability converts odds into a percentage that represents how likely the sportsbook believes an outcome is to occur. This is one of the most important concepts in sports betting because it lets you compare the sportsbook's assessment against your own.
Implied Probability Formulas
| Odds Format | Formula | Example |
|---|---|---|
| American (−) | Odds ÷ (Odds + 100) × 100 | -150 → 150 ÷ 250 = 60.0% |
| American (+) | 100 ÷ (Odds + 100) × 100 | +130 → 100 ÷ 230 = 43.5% |
| Decimal | (1 ÷ Decimal Odds) × 100 | 1.80 → 1 ÷ 1.80 = 55.6% |
| Fractional | Denominator ÷ (Numerator + Denominator) × 100 | 7/2 → 2 ÷ 9 = 22.2% |
Notice something important: if you add the implied probabilities for both sides of a two-way market, the total will exceed 100%. That extra percentage is the vig (or juice)—the sportsbook's built-in profit margin.
Example: Chiefs -150 (60.0%) + Bills +130 (43.5%) = 103.5%. The extra 3.5% is the vig.
Converting Between Odds Formats
Here's a quick reference table for converting between the three formats:
| American | Decimal | Fractional | Implied Probability |
|---|---|---|---|
| -300 | 1.33 | 1/3 | 75.0% |
| -200 | 1.50 | 1/2 | 66.7% |
| -150 | 1.67 | 2/3 | 60.0% |
| -110 | 1.91 | 10/11 | 52.4% |
| +100 | 2.00 | 1/1 | 50.0% |
| +110 | 2.10 | 11/10 | 47.6% |
| +150 | 2.50 | 3/2 | 40.0% |
| +200 | 3.00 | 2/1 | 33.3% |
| +300 | 4.00 | 3/1 | 25.0% |
| +500 | 6.00 | 5/1 | 16.7% |
Conversion Formulas
American to Decimal:
- Negative: (Odds + 100) ÷ Odds → -150 → 250 ÷ 150 = 1.667
- Positive: (Odds + 100) ÷ 100 → +200 → 300 ÷ 100 = 3.00
Decimal to American:
- If decimal ≥ 2.00: (Decimal − 1) × 100 → 3.00 → +200
- If decimal < 2.00: −100 ÷ (Decimal − 1) → 1.50 → -200
Which Sportsbooks Use Which Format?
In the US market, American odds are the default on virtually every major sportsbook, including DraftKings, FanDuel, BetMGM, Caesars Sportsbook, PointsBet, BetRivers, and Fanatics Sportsbook. However, most platforms let you switch to decimal or fractional odds in your account settings.
Internationally, decimal odds dominate on platforms like Bet365, Pinnacle, and Betfair. UK-based bookmakers like William Hill, Ladbrokes, and Paddy Power traditionally display fractional odds but also offer decimal.
How WagerWiz Displays and Compares Odds
WagerWiz displays American odds by default to match the US sportsbook standard, with an option to toggle to decimal odds. More importantly, WagerWiz's real power lies in comparing odds across dozens of sportsbooks simultaneously.
When you're looking at an NFL spread, for example, WagerWiz will show you the best available line at each sportsbook side by side. If DraftKings has the Chiefs at -148 while FanDuel has them at -155, you instantly know where to place your bet for the best value. Over hundreds of bets, consistently grabbing the best line adds up to a significant edge.
WagerWiz also calculates implied probability and identifies the no-vig fair odds for every market, so you can immediately see whether a sportsbook's line offers positive expected value.
FAQ
What does -110 mean in betting?
Odds of -110 mean you need to bet $110 to win $100 in profit. This is the standard pricing for point spread and totals bets at most US sportsbooks. The extra $10 you risk beyond your potential profit represents the vig—the sportsbook's commission on the wager.
Are decimal odds better than American odds?
Neither format is inherently better—they convey the same information. Decimal odds are simpler for quick mental math (just multiply your stake by the number), while American odds clearly distinguish favorites from underdogs at a glance. Many experienced bettors prefer decimal because comparing small differences between lines is easier. Use whichever format you're most comfortable with.
How do I know if odds represent good value?
Odds represent good value when the implied probability they reflect is lower than the actual probability of the outcome. For example, if a team is priced at +150 (implied 40%) but you believe they have a 50% chance of winning, that's a value bet with positive expected value. WagerWiz automates this process by calculating fair odds from the market and flagging lines that offer +EV.
Why do odds change before a game starts?
Odds move for several reasons: sharp bettors placing large wagers, injury news (like an NBA star being ruled out), weather changes (especially for NFL and MLB), and general public betting patterns. Sportsbooks adjust lines to balance their risk. Early odds often differ significantly from closing lines, which is why line shopping with a tool like WagerWiz is so valuable.
What is the vig, and how does it relate to odds?
The vig (also called juice) is the sportsbook's built-in margin on every bet. You can see it by converting both sides of a market to implied probability and adding them together. If the total exceeds 100%, the overage is the vig. A standard -110/-110 market has about 4.5% vig. Lower vig means better odds for the bettor, which is why comparing across sportsbooks matters.
