How to Convert Betting Odds: American, Decimal, Fraction

Converting betting odds means rewriting the same price in another format, because American, decimal, and fractional odds all describe one probability and just display it differently. The favorite priced at -200 is 1.50 in decimal, 1/2 in fractional, and a 66.7% implied chance, all at once. Learn one short formula for each direction and you can move any price into the format you read fastest, or into a clean percentage you can actually judge. The betting odds converter does every format in a second, and this guide shows the math behind it so you can check the tool or run the numbers yourself.

American, decimal, and fractional: what each format shows

Three formats dominate betting, one probability underneath. Here is what each one is actually telling you.

American odds

American odds use a plus or minus sign. A negative number is the favorite and shows how much you stake to win $100, so -200 means risk $200 to win $100. A positive number is the underdog and shows how much you win on a $100 stake, so +150 means a $100 bet returns $150 profit. The sign tells you the side, the number tells you the price.

Decimal odds

Decimal odds show your total return per $1 staked, stake included. A price of 2.50 returns $2.50 for every $1, which is $1.50 profit plus your $1 back. Decimal is the cleanest format for payout math, since you just multiply your stake by the number.

Fractional odds

Fractional odds show profit over stake. A price of 3/2 pays $3 profit for every $2 staked. Written as numerator over denominator, the left number is what you win, the right is what you risk. Fractional is common in horse racing and UK markets.

How to convert between the three formats

Each direction is one line of arithmetic. These are the ones worth knowing.

American to decimal

• Positive odds: decimal = (odds / 100) + 1. So +150 becomes (150 / 100) + 1 = 2.50.
• Negative odds: decimal = (100 / |odds|) + 1. The bars mean you drop the minus sign first, so -200 becomes (100 / 200) + 1 = 1.50.

Decimal to American

• Decimal of 2.00 or higher: American = (decimal - 1) x 100. So 2.50 becomes (2.50 - 1) x 100 = +150.
• Decimal below 2.00: American = -100 / (decimal - 1). So 1.50 becomes -100 / 0.50 = -200.

American and decimal to fractional

From American, a positive price is odds / 100 reduced to a fraction, so +150 is 150/100 = 3/2. A negative price is 100 / |odds| reduced, so -200 is 100/200 = 1/2. From decimal, subtract 1 and write the result as a fraction, so 2.50 becomes 1.5, which is 3/2. All three roads meet at the same fraction.

How to convert odds to implied probability

The most useful conversion is not between formats, it is into a percentage, because a percentage is the win rate the price is asking you to beat. Use the formula for the format in front of you:

• Decimal: probability = 1 / decimal. So 2.50 = 1 / 2.50 = 40%.
• Negative American: probability = |odds| / (|odds| + 100). So -200 = 200 / 300 = 66.7%.
• Positive American: probability = 100 / (odds + 100). So +150 = 100 / 250 = 40%.
• Fractional: probability = denominator / (numerator + denominator). So 3/2 = 2 / 5 = 40%.

For a deeper walk through this step, see odds to percentage, and to go the other way and turn a percentage back into a fair price, use the implied probability calculator.

One price, every format: a worked example

Take an underdog at +150 and run it through everything so you can see the formats line up:

• American: +150.
• Decimal: (150 / 100) + 1 = 2.50.
• Fractional: 150 / 100 = 3/2.
• Implied probability: 100 / (150 + 100) = 40%.

Every one of those is the same bet. A $100 stake wins $150 profit, the market thinks it hits 40% of the time, and whether your screen shows +150, 2.50, or 3/2, the price never changed. If American odds are your default, the American odds guide breaks down how the plus and minus prices read before you convert anything.

The number the format hides

Converting formats is cosmetic. Converting to a percentage exposes the one thing that actually costs you money: the margin. Add up the implied percentages on both sides of a standard -110 market and you get 52.4% plus 52.4%, which is 104.8%. That extra 4.8% is the house fee baked into the price, the reason the two sides do not sum to a clean 100%. No format change removes it, because it lives in the number itself.

That is the difference at BettorEdge. It is a peer-to-peer betting marketplace where you take community odds against other real bettors with no built-in vig padding the line, so the price you convert is much closer to the true one. Whatever format you read in, the number is fairer to begin with. Sign up on BettorEdge and bet peer to peer at community odds, so the price you just converted is the real one.

How to convert betting odds FAQ

How do you convert betting odds between formats?

Use one formula per direction. For American to decimal, positive odds are (odds / 100) + 1 and negative odds are (100 / the odds without the sign) + 1. For decimal to American, a decimal of 2.00 or more is (decimal - 1) x 100, and below 2.00 it is -100 / (decimal - 1). For fractional, a positive American price is odds/100 reduced, and decimal minus 1 written as a fraction gives the same result.

What is +150 in decimal and fractional odds?

+150 American equals 2.50 in decimal and 3/2 in fractional. The decimal comes from (150 / 100) + 1 = 2.50, and the fraction from 150 / 100 = 3/2. All three represent a 40% implied probability and pay $150 profit on a $100 stake.

How do you convert decimal odds to American odds?

For a decimal price of 2.00 or higher, American odds equal (decimal - 1) x 100, so 2.50 becomes +150. For a decimal below 2.00, American odds equal -100 / (decimal - 1), so 1.50 becomes -200. The 2.00 break point is even money, where decimal 2.00 equals American +100.

What is the easiest odds format to work with?

Decimal odds are the easiest to work with. Your total return is simply stake times the decimal, so $10 at 2.50 returns $25. Converting decimal to a percentage is also one step, 1 divided by the decimal, which makes it the quickest format for judging value.

How do you convert odds to a percentage?

Divide to find the implied probability. For decimal, it is 1 / decimal. For negative American odds, it is the odds without the sign divided by that number plus 100. For positive American odds, it is 100 divided by the odds plus 100. For fractional, it is the denominator divided by the sum of both numbers.

Do different odds formats change the payout?

No. The format is only a display choice, so +150, 2.50, and 3/2 all pay exactly the same. A $100 bet wins $150 profit at every one of them. Converting between formats never changes your payout or the implied probability, it only changes how the price is written.