Odds Converter

What is an odds converter?

Sportsbooks across the world use different formats to display odds. American odds dominate the US, decimal odds are standard in Europe and most of the rest of the world, fractional odds are traditional in UK horse racing and British high-street shops, and implied probability is what every one of them really means underneath.

The numbers all describe the same thing. A line of -110 is the same as 1.91 decimal, 10/11 fractional, and 52.38% implied probability. Being able to flip between formats is useful when you're comparing prices across books, reading strategy content from another country, or checking how much edge a line actually carries.

The four formats, side by side

American odds use +/- pricing. A negative number is the amount you'd need to risk to win $100. A positive number is the amount you'd win from a $100 stake. -150 means risk $150 to win $100. +150 means risk $100 to win $150.

Decimal odds show your total return per unit staked, including your stake back. Decimal 2.50 means a $1 bet pays $2.50 total, for $1.50 profit. Decimal 1.50 means a $1 bet pays $1.50, for $0.50 profit.

Fractional odds show profit over stake. 3/1 (spoken "three to one") means you'd win $3 for every $1 staked. 1/2 means you'd win $1 for every $2 staked. Fractional is the least-precise format and gets ugly fast when the true number doesn't simplify nicely.

Implied probability is what the odds are really saying about the likelihood of the outcome. A line of -110 implies the sportsbook thinks this outcome happens about 52.38% of the time, once you back out the vig. This is the number that actually matters for evaluating whether a bet has positive expected value.

How the math works

Each format has a simple formula relating it to decimal odds, which is the cleanest working format:

• American (positive) to decimal: (odds / 100) + 1. So +150 becomes 2.50.
• American (negative) to decimal: (100 / |odds|) + 1. So -150 becomes 1.6667.
• Fractional to decimal: (numerator / denominator) + 1. So 3/2 becomes 2.50.
• Decimal to implied probability: (1 / decimal) × 100. So 2.50 becomes 40%.

Related reading

The sports betting odds guide walks through each format in more depth. The expected value guide shows how implied probability turns into an edge. The no-vig calculator uses these formulas to strip the sportsbook's margin out of a line.