Fractional Odds

Fractional odds are the traditional UK format. They look like 5/2 or 10/11, where the first number is the profit you’d win and the second is the stake you’d risk. The format is most common at British bookmakers and on horse racing tracks worldwide.

How to read fractional odds

The fraction is profit / stake. Bet the bottom number, win the top number (plus your stake back).

• 1/1 (read “one-to-one”) — even money. Bet $10, win $10. Total payout $20.
• 5/2 (“five to two”) — bet $2 to win $5. $10 bet → $25 profit, $35 total payout.
• 10/11 (“ten to eleven”) — slight favorite. Bet $11 to win $10. The standard British vig line.
• 3/1 — bet $1 to win $3. Heavy underdog.
• 1/4 — bet $4 to win $1. Heavy favorite.

The bottom number being larger than the top means you’re betting a favorite; the top being larger means you’re betting an underdog.

Converting to decimal

decimal = (numerator / denominator) + 1.

• 5/2 → 5/2 + 1 = 3.50
• 10/11 → 10/11 + 1 ≈ 1.91 (this is exactly equivalent to -110 American)
• 1/4 → 0.25 + 1 = 1.25

Implied probability

probability = denominator / (numerator + denominator).

• 5/2 → 2/7 = 28.6%
• 10/11 → 11/21 = 52.4%
• 1/4 → 4/5 = 80.0%

When you’ll see it

Horse racing in the US still uses fractional odds for “morning lines” and pari-mutuel pools. UK and Irish sportsbooks default to fractional, though most apps now offer decimal as a toggle. Some niche markets (futures, longshots) at US books still post fractional alongside the moneyline.