Decimal odds are not commonly used in American betting, but are the most common odds around the world. As opposed to American odds which are based on a $100 bet, decimal odds just give you the total return (risk included) for every $1 wagered. It’s a simpler system than American odds because the same formula is used to calculate the implied probability, payouts, etc. of the bet winning. As explained in the American odds article, a different formula is needed to calculate everything.

In this game, we can see the Moneyline odds for Boston to win is 2.33, and Dallas to win is 1.75. The point spread for Boston is 1.95 odds, vs 1.91 from Dallas.

What does that mean?

The standard American odds point spread price is -110 where risking $110 wins $100. With decimal odds, it’s based on every $1 wagered. For the NFL listings above that say 1.91, every $1 risked wins $0.91 which returns $1.91.

Clearly, it returns the exact same amount as a -110 listing in American odds – $1*(100/-110*-1) = $0.91 +$1 stake returns the same $1.91.

The best part of using decimal odds is how simple the calculations are with your bets. The formula (if you can even call it that) is just multiplying the decimal odds by the amount you wagered.

If you can only find decimal odds and want to make sure they’re right for you with the more familiar American odds, here is how to make the conversion.

It’s a little complicated because American odds have a plus and minus to indicate favorite and underdog.

When you see decimal odds of 2.0 or higher (meaning it will be positive in American odds), use this formula:
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For example, 2.5 decimal odds would become (2.5 - 1) * 100 = +150

To convert back from American to decimal odds for positive odds, use this formula:

As you can see, 1 + (150/100) = 2.5 and we are back at 2.5.

We have a different formula for negative American odds, or decimal odds under 2.0.

To convert from decimal odds under 2.0 to American odds, use this formula:

For decimal odds of 1.5, it would be (-100) / (1.5-1) which equals -200, so the American odds are -200.

To convert it back, we would use this formula:

For American odds of -200 it would be: 1 – (100/-200) which simplifies to 1 + 0.5 and we are back to 1.5.

Fractional odds are mainly used in the UK, as well as Ireland. This odds format shows the potential profit should the bet win, quoted as a fraction of the stake. These odds are most commonly seen in horse racing.

Converting decimal odds to fractional odds is simple. Just subtract 1.00 and reduce that number to its simplest fraction.

For example, for decimal odds of 1.2 subtract 1.0, and now you’re left with 0.2.

0.2 is ⅕, which is the fractional odds.

To convert back to decimal odds, just divide the fractions (⅕ = 0.2) and add 1.0.

The 1.0 subtracted and added in the conversion represents your stake in the decimal odds.

OddsJam has a very convenient odds converter calculator you can use to easily convert any type of odds to any other, as well as showing implied win probability.
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