Fractional Odds Explained

Fractional odds are the traditional odds format used across the United Kingdom and Ireland. If you have ever seen odds displayed as 5/1, 3/2, or 1/4 at a bookmaker, you have encountered fractional odds. They remain the default format at most UK and Irish sportsbooks and are deeply rooted in horse racing.

This guide explains how fractional odds work, how to calculate payouts and profit, and how they compare to American odds and decimal odds. Whether you are placing your first bet or trying to understand odds from a UK sportsbook, fractional odds are straightforward once you learn the basics.

What Are Fractional Odds?

Fractional odds represent your potential profit relative to your stake. They are written as two numbers separated by a slash, such as 5/1, 3/2, or 1/4. The first number (numerator) tells you how much profit you win, and the second number (denominator) tells you how much you need to stake.

For example, fractional odds of 5/1 (spoken as "five to one") mean that for every 1 dollar you stake, you win 5 dollars in profit. You also get your original stake back, so a 1 dollar bet at 5/1 returns 6 dollars total.

Fractional odds fall into three categories:

• Odds-against (numerator larger than denominator): You win more than you stake. Examples: 5/1, 3/1, 2/1, 6/4
• Even money (1/1): You win exactly the amount you stake. A 100 dollar bet returns 200 dollars total
• Odds-on (numerator smaller than denominator): You win less than you stake. Examples: 1/2, 1/3, 4/9

This format originated in British horse racing and has been used for centuries. While decimal odds have become more common internationally, fractional odds remain the preferred format for many UK bettors and at traditional bookmakers.

How to Read Fractional Odds

Reading fractional odds comes down to one rule: the first number is your profit, and the second number is your stake. Think of the slash as "to" when reading them aloud.

Here are common examples:

• 5/1 (five to one) means 5 dollars profit for every 1 dollar staked
• 3/1 (three to one) means 3 dollars profit for every 1 dollar staked
• 2/1 (two to one) means 2 dollars profit for every 1 dollar staked
• 1/1 (evens) means 1 dollar profit for every 1 dollar staked
• 1/2 (one to two) means 1 dollar profit for every 2 dollars staked
• 1/4 (one to four) means 1 dollar profit for every 4 dollars staked

When the first number is larger, the outcome is considered unlikely and the potential payout is higher. When the second number is larger, the outcome is considered likely and the payout is smaller relative to your stake.

Fractional Odds	Type	$100 Bet Profit	$100 Bet Total Return
10/1	Odds-against	$1,000	$1,100
5/1	Odds-against	$500	$600
3/1	Odds-against	$300	$400
2/1	Odds-against	$200	$300
6/4	Odds-against	$150	$250
1/1	Even money	$100	$200
1/2	Odds-on	$50	$150
1/4	Odds-on	$25	$125

Calculating Payouts and Profit with Fractional Odds

Fractional odds make profit calculations intuitive because the fraction itself tells you the ratio. For exact amounts, use these formulas:

Profit = Stake x (Numerator / Denominator)

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

Example 1: Betting on an Underdog at 5/1

You bet 50 dollars on a team at fractional odds of 5/1.

Profit = 50 x (5 / 1) = 50 x 5 = 250 dollars

Total Return = 250 + 50 = 300 dollars

Example 2: Betting on a Favorite at 1/3

You bet 90 dollars on a heavy favorite at fractional odds of 1/3.

Profit = 90 x (1 / 3) = 90 x 0.333 = 30 dollars

Total Return = 30 + 90 = 120 dollars

Example 3: Betting at Non-Standard Odds of 6/4

You bet 100 dollars at fractional odds of 6/4.

Profit = 100 x (6 / 4) = 100 x 1.5 = 150 dollars

Total Return = 150 + 100 = 250 dollars

Note that 6/4 is the same as 3/2. Fractional odds are not always simplified to their lowest terms, particularly in horse racing. You may see 6/4 instead of 3/2, or 5/2 instead of 2.5/1. The payout is identical regardless of how the fraction is expressed.

With decimal odds, you multiply your stake by a single number to get the total return. Fractional odds require one extra step because they show profit only, not total return. For a deeper comparison, see our odds conversion guide.

Use Our Odds Converter Calculator

The fastest way to work with fractional odds is to use our Odds Converter Calculator. Enter any fractional odds value and instantly see the equivalent in American and decimal formats, plus the implied probability.

You can also enter American or decimal odds and convert them to fractional format. The calculator shows your exact profit and total return for any stake amount.

Converting Fractional Odds to Implied Probability

Every set of odds represents an implied probability: the likelihood the sportsbook assigns to that outcome. Converting fractional odds to implied probability uses a simple formula.

Implied Probability = Denominator / (Numerator + Denominator) x 100

Example: What is the implied probability of 3/1?

Probability = 1 / (3 + 1) x 100 = 1 / 4 x 100 = 25%

The sportsbook estimates a 25% chance of this outcome occurring.

Example: What is the implied probability of 1/3?

Probability = 3 / (1 + 3) x 100 = 3 / 4 x 100 = 75%

The sportsbook estimates a 75% chance of this outcome occurring.

Fractional Odds	Implied Probability	Interpretation
1/5	83.3%	Heavy favorite
1/3	75%	Strong favorite
1/2	66.7%	Clear favorite
10/11	52.4%	Slight favorite (standard vig line)
1/1	50%	Even money
6/4	40%	Moderate underdog
2/1	33.3%	Clear underdog
4/1	20%	Significant longshot
9/1	10%	Major longshot

Understanding implied probability helps you identify value bets. If you believe a team has a 50% chance of winning but the fractional odds are 6/4 (implying only 40%), that gap represents positive expected value. For a complete guide on converting between all odds formats, see our odds conversion guide.

Fractional Odds vs American and Decimal Odds

Fractional odds are one of three main formats used in sports betting. Here is how the same probabilities look across all three formats:

Fractional	Decimal	American	Implied Probability
1/3	1.33	-300	75%
1/2	1.50	-200	66.7%
2/3	1.67	-150	60%
10/11	1.91	-110	52.4%
1/1 (evens)	2.00	+100	50%
3/2	2.50	+150	40%
2/1	3.00	+200	33.3%
3/1	4.00	+300	25%

American odds use positive and negative numbers centered around 100 dollars. Positive odds show profit on a 100 dollar bet, while negative odds show how much you must bet to win 100 dollars. They are the standard at US sportsbooks.

Decimal odds display a single number that represents your total return per unit staked, including your original stake. They are the default on most international sportsbooks and betting exchanges because one multiplication gives you the total return.

Fractional odds show profit relative to stake as a fraction. They are traditional in UK and Irish betting, particularly horse racing. Comparing fractional odds can require more mental math than decimal format, but they clearly communicate the profit-to-stake ratio.

If you bet across different platforms, you will encounter all three formats. Our odds conversion guide covers every conversion formula, and the odds converter calculator handles conversions instantly.

Common Fractional Odds You Will See

Certain fractional odds appear frequently at UK and Irish sportsbooks. Recognizing these values helps you assess opportunities faster.

10/11: The Standard Vig Line

Most point spreads and totals at UK sportsbooks are priced at 10/11 on both sides. This is the fractional equivalent of -110 in American odds or 1.91 in decimal. The implied probability is 52.4%, and when both sides are at 10/11, the combined probability is 104.8%. That extra 4.8% is the sportsbooks margin.

1/1: Even Money (Evens)

Even money means your profit equals your stake. A 100 dollar bet returns 200 dollars total (100 dollars profit). The implied probability is 50%. You will often hear this referred to simply as "evens."

1/2: Strong Favorite

Fractional odds of 1/2 represent a clear favorite with a 66.7% implied probability. This is the fractional equivalent of -200 in American odds or 1.50 in decimal. A 100 dollar bet returns 150 dollars total (50 dollars profit).

2/1: Clear Underdog

At 2/1, a 100 dollar bet returns 300 dollars total (200 dollars profit). The implied probability is 33.3%, equivalent to +200 in American odds or 3.00 in decimal. This is a common price for underdogs in two-way markets.

Why UK Bookmakers Still Use Fractional Odds

Fractional odds are deeply embedded in British and Irish betting culture, especially in horse racing where odds like 11/4, 9/2, and 100/30 are called out by on-course bookmakers. Many UK bettors grew up reading fractional odds and find them intuitive. Most modern UK sportsbooks now let you switch between formats in your account settings, and some display decimal odds by default for new accounts.

Tips for Working with Fractional Odds

Use evens (1/1) as your mental anchor. Just as +100 is the reference point for American odds and 2.00 for decimal, 1/1 is the dividing line for fractional odds. Anything with a larger numerator is odds-against (underdog), anything with a larger denominator is odds-on (favorite).

Remember that fractional odds show profit only. Unlike decimal odds which include your stake in the return, fractional odds only tell you the profit. Odds of 1/2 mean 0.50 units of profit per unit staked, not 0.50 units total return. Your total return is always your profit plus your stake.

Convert to decimal for quick comparison. To convert fractional odds to decimal, divide the numerator by the denominator and add 1. So 5/2 becomes (5 / 2) + 1 = 3.50 in decimal. This is useful when comparing prices across sportsbooks that use different formats.

Watch for non-reduced fractions. In horse racing, you will see odds like 100/30 instead of 10/3, or 6/4 instead of 3/2. The payouts are identical. Sportsbooks and on-course bookmakers use these traditional forms out of convention.

Learn the common equivalents. Knowing that 10/11 equals -110, 1/1 equals +100, and 2/1 equals +200 helps you navigate between UK and US sportsbooks. Use our odds converter tool when you need to convert quickly.

Frequently Asked Questions

What are fractional odds in betting?

Fractional odds are a format that shows your potential profit relative to your stake. They are written as two numbers separated by a slash, such as 5/1 or 3/2. The first number represents your profit, and the second represents the amount you need to stake. For example, 5/1 means you win 5 dollars profit for every 1 dollar staked. They are the traditional format in the United Kingdom and Ireland.

How do I calculate my payout with fractional odds?

Divide the first number by the second number, then multiply by your stake to get your profit. Add your original stake for the total return. For example, a 100 dollar bet at 3/1 returns 300 dollars in profit plus your 100 dollar stake, for 400 dollars total. A 100 dollar bet at 1/2 returns 50 dollars in profit plus your 100 dollar stake, for 150 dollars total.

What does 5/1 mean in betting?

Fractional odds of 5/1 (five to one) mean you win 5 dollars in profit for every 1 dollar you stake. On a 100 dollar bet, you would win 500 dollars in profit and receive 600 dollars total (profit plus your original stake). The implied probability is 16.7%, making this a significant underdog. In American odds, 5/1 is equivalent to +500.

How do I convert fractional odds to decimal odds?

Divide the numerator by the denominator and add 1. For example, 3/1 becomes (3 / 1) + 1 = 4.00 in decimal. And 1/2 becomes (1 / 2) + 1 = 1.50 in decimal. The decimal format includes your stake in the total return, while fractional shows profit only. Our odds conversion guide covers all conversion formulas in detail.

What does odds-on mean?

Odds-on means the denominator is larger than the numerator, such as 1/2, 1/3, or 4/9. It indicates a favorite where you win less profit than you stake. At 1/2, you need to bet 2 dollars to win 1 dollar in profit. Odds-on outcomes have an implied probability above 50%. The opposite is odds-against, where you win more than you stake.

Are fractional odds still used in sports betting?

Yes, fractional odds remain the default format at most UK and Irish sportsbooks, particularly for horse racing. They are deeply embedded in British betting culture. However, many international sportsbooks and betting exchanges use decimal odds as their default, and most platforms allow you to switch between formats in your settings.

What is the difference between fractional and decimal odds?

Fractional odds show only your profit relative to your stake (e.g., 3/2 means 1.50 dollars profit per 1 dollar staked). Decimal odds show your total return including your stake (e.g., 2.50 means 2.50 dollars total return per 1 dollar staked). Both represent the same probability, just displayed differently. Many bettors find decimal odds easier for quick comparisons, while fractional odds are traditional in UK markets.

What does evens mean in betting?

Evens is another way of saying 1/1 in fractional odds. It means your profit equals your stake. A 100 dollar bet at evens returns 200 dollars total (100 dollars profit plus your 100 dollar stake). The implied probability is 50%. Evens is equivalent to +100 in American odds or 2.00 in decimal odds.