How to Read Betting Odds: American, Decimal & Fractional

The Three Odds Formats

Sportsbooks around the world use three different formats to display the same information. Understanding all three, and how to convert between them, is fundamental to sports betting.

All three formats express the same thing: the ratio of profit to stake and the implied probability of an outcome. You can compare odds across sportsbooks to see these formats in action across 400+ bookmakers. If you're specifically wondering about what moneyline means, we have a dedicated guide for that.

American Odds (Moneyline)

American odds use a positive or negative number relative to $100.

Negative Odds (Favorites)

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

• -150 means you bet $150 to win $100 profit (total return: $250)
• -300 means you bet $300 to win $100 profit (total return: $400)
• -110 means you bet $110 to win $100 profit (total return: $210)

The larger the negative number, the heavier the favorite.

Positive Odds (Underdogs)

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

• +200 means you win $200 profit on a $100 bet (total return: $300)
• +150 means you win $150 profit on a $100 bet (total return: $250)
• +500 means you win $500 profit on a $100 bet (total return: $600)

The larger the positive number, the bigger the underdog.

Calculating Payout from American Odds

For negative odds:

Payout = Stake x (100 / |Odds|) + Stake

Example: $50 bet at -150 → $50 x (100/150) + $50 = $83.33

For positive odds:

Payout = Stake x (Odds / 100) + Stake

Example: $50 bet at +200 → $50 x (200/100) + $50 = $150

What the Plus and Minus Signs Mean

The plus (+) sign marks an underdog and shows how much profit you win on a $100 bet. The minus (-) sign marks a favorite and shows how much you need to risk to win $100 in profit. The bigger the number in either direction, the more lopsided the matchup.

• -120 means you risk $120 to win $100. A slight favorite.
• +200 means you win $200 on a $100 bet. The sportsbook considers this outcome unlikely.
• -300 means you risk $300 to win $100. A heavy favorite with roughly 75% implied probability.
• +100 means even money. Both sides are equally likely according to the book.

Decimal Odds

Decimal odds show your total return per dollar wagered (including your stake).

• 1.50 means $1 bet returns $1.50 total ($0.50 profit)
• 2.00 means $1 bet returns $2.00 total ($1.00 profit, which is even money)
• 3.50 means $1 bet returns $3.50 total ($2.50 profit)

Why Decimal Is the Simplest Format

The payout calculation is just multiplication:

Total Return = Stake x Decimal Odds
Profit = Stake x (Decimal Odds - 1)

Example: $75 bet at 2.40 → Total return = $75 x 2.40 = $180. Profit = $105.

Decimal odds also make it easy to compare value across markets. The higher the decimal odds, the bigger the payout, with no mental gymnastics with negative signs.

Fractional Odds

Fractional odds show the ratio of profit to stake.

• 2/1 (two-to-one) means $2 profit per $1 staked
• 1/2 (one-to-two) means $1 profit per $2 staked
• 5/4 (five-to-four) means $5 profit per $4 staked

Calculating Payout from Fractional Odds

Profit = Stake x (Numerator / Denominator)
Total Return = Profit + Stake

Example: $40 bet at 5/2 → Profit = $40 x (5/2) = $100. Total return = $140.

Fractional odds are most common in UK horse racing and traditional British sportsbooks. For sports betting analysis, decimal or American are more practical. Once you understand odds formats, you can explore multi-bet options like round robin bets that combine selections into multiple smaller parlays.

Converting Between Formats

American to Decimal

For negative American:

Decimal = 1 + (100 / |American|)

Example: -150 → 1 + (100/150) = 1.667

For positive American:

Decimal = 1 + (American / 100)

Example: +200 → 1 + (200/100) = 3.00

Decimal to American

If decimal < 2.00 (favorite):

American = -100 / (Decimal - 1)

Example: 1.50 → -100 / (1.50 - 1) = -200

If decimal >= 2.00 (underdog or even):

American = (Decimal - 1) x 100

Example: 3.00 → (3.00 - 1) x 100 = +200

Quick Reference Table

Reading Odds in Practice: Real Examples

Textbook definitions only get you so far. Here's how odds actually appear on sportsbooks, and what they mean for your bet.

NFL Spread: Eagles -3.5 (-110)

You see "Eagles -3.5 (-110)" on DraftKings. This means two things at once. The -3.5 is the point spread: the Eagles need to win by 4 or more points for your bet to cash. The -110 is the price you pay on that spread: risk $110 to win $100 in profit. Nearly all spread bets in the NFL are priced around -110 on both sides, which is how the sportsbook builds in its margin.

NBA Moneyline: Celtics -180 / Lakers +150

On a moneyline bet, you're picking the outright winner with no point spread involved. Celtics -180 means you risk $180 to win $100 because the Celtics are the favorite. Lakers +150 means a $100 bet on the Lakers returns $150 in profit if they pull the upset. The gap between -180 and +150 is the sportsbook's margin. If there were no margin, a -180 favorite would have the underdog priced at +180.

Soccer 3-Way: Man City 1.45 / Draw 4.50 / Liverpool 6.00

Soccer moneylines have three possible outcomes because games can end in a draw. Man City at 1.45 (decimal) means a $100 bet returns $145 total, so just $45 profit. They're heavy favorites. Draw at 4.50 pays $350 profit on $100, reflecting how draws are uncommon but not rare. Liverpool at 6.00 pays $500 profit on $100, making them significant underdogs. All three outcomes have separate odds, and you only win if your specific pick is correct.

Understanding Spread Odds

Spread betting (also called point spread or handicap betting) is the most popular way to bet on football and basketball. The spread levels the playing field between a favorite and an underdog by assigning a point handicap.

Every spread bet has two components: the spread itself (the points) and the odds on the spread (usually -110).

Example: Bills -6.5 (-110) means you need the Bills to win by 7 or more points for your bet to win. You risk $110 to win $100 in profit. The opposing line would be something like "Dolphins +6.5 (-110)," meaning the Dolphins can lose by up to 6 points and you still win.

The half-point (.5) eliminates the possibility of a push (tie against the spread). When the spread is a whole number like -7, the game can land exactly on that number, and your bet is refunded.

Why are both sides usually -110? The sportsbook wants equal money on both sides. The difference between what losers pay ($110) and what winners receive ($100) is the sportsbook's built-in profit. If money comes in lopsided, the book may shift the spread or adjust the odds to -115 on one side and -105 on the other.

Implied Probability

Every set of odds implies a probability of the outcome occurring. This is the most important concept for identifying value.

From Decimal Odds

Implied Probability = 1 / Decimal Odds

Example: 2.50 → 1 / 2.50 = 40%

From American Odds

Negative:

Implied Probability = |American| / (|American| + 100)

Example: -150 → 150 / 250 = 60%

Positive:

Implied Probability = 100 / (American + 100)

Example: +200 → 100 / 300 = 33.3%

Why Implied Probability Matters

Implied probability tells you what the sportsbook thinks the chance of an outcome is (including their margin). If you believe the true probability is higher than what the odds imply, you've found a value bet.

For example, if a team is priced at +200 (implied 33.3%) but you calculate their true probability is 40%, the odds are in your favor. That's a +EV bet.

To get the true probability without the bookmaker's margin, you need to remove the vig.

Common Odds Scenarios

Even Money

• American: +100
• Decimal: 2.00
• Fractional: 1/1 (also called "evens")
• Implied: 50%

A $100 bet returns $200 (your $100 stake + $100 profit).

Heavy Favorite

• American: -300
• Decimal: 1.33
• Fractional: 1/3
• Implied: 75%

You need to risk $300 to win $100. The market thinks this outcome happens 3 out of 4 times.

Big Underdog

• American: +500
• Decimal: 6.00
• Fractional: 5/1
• Implied: 16.7%

A $100 bet returns $600. The market thinks this outcome happens about 1 in 6 times.

Key Takeaways

• American odds show profit relative to $100, with negative for favorites and positive for underdogs
• Decimal odds show total return per dollar and are the simplest format for calculations
• Fractional odds show profit-to-stake ratio and are mostly used in UK markets
• Implied probability is the most important concept because it reveals what the odds actually mean
• All three formats are equivalent. Use whichever you're comfortable with, but understand all of them
• Use an odds converter if you need to switch between formats quickly
• New to betting? Our sports betting for beginners guide covers everything you need to get started