Odds formats: decimal, fractional, American

Three ways of writing, one single price

An odd can be written in decimal, fractional or American format. These three notations describe exactly the same price. What changes is what the figure on display counts: the total return, the net profit, or a reference stake of 100.

The point to hold on to before anything else: the implied probability does not depend on the format. An odd of 2.50 is worth 40% whether it is written 2.50, 3/2 or +150.

The decimal odd

The decimal odd gives the total return for one unit staked, stake included. It is the format used by operators licensed in France, and the one used by every calculator on this site.

An odd of 2.50 returns €2.50 for €1 staked, of which €1 is the stake handed back: the net profit is €1.50. An odd of 1.50 returns €1.50, of which €0.50 is net profit.

Its readability comes from that: the amount displayed can be multiplied straight by the stake, with no intermediate conversion. Its implied probability is read with a single division, 1 ÷ odd, as detailed on implied probability.

The fractional odd

The fractional odd gives the net profit, not the total return. It is traditionally used in the United Kingdom and Ireland.

An odd of 3/2 means 3 units won for 2 units staked. For €10 committed: €15 of net profit, €25 of total return. The equivalent decimal odd is 3 ÷ 2 + 1 = 2.50.

The + 1 in the conversion is the most frequent source of error. An odd of 1/1, often called “even money”, is worth 2.00 in decimal and not 1.00: the stake comes back on top of the profit.

The American odd

The American odd is read differently depending on its sign, and that sign has nothing to do with a profit or a loss.

A positive odd gives the net profit for 100 staked. +150 means 150 of net profit for 100 committed, that is a decimal odd of 2.50.

A negative odd gives the stake needed to win 100 of net profit. −200 means you have to stake 200 to win 100, that is a decimal odd of 1.50.

The threshold between the two notations is the decimal odd 2.00, that is an implied probability of 50%. Above it, the American odd is positive; below it, negative. An odd of exactly 2.00 is written +100.

The equivalence table

The same prices, written in all four units. This table is generated from the conversion engine used by the site's calculators: the values displayed here are the ones the tools produce.

Fractional odds are readable approximations: 4/5 corresponds to 1.80 exactly, but not every decimal odd falls on a simple fraction. That is a limit of the format, not of the calculation.

Convert an odd into all four units →

The most common reading errors

Three confusions come up constantly, and two of them cost money.

Confusing net profit and total return. A decimal odd of 3.00 does not pay three times the stake in profit: it returns three times the stake in total, of which one is the stake itself. The net profit is two times the stake. The matching fractional odd, 2/1, states that net profit directly — hence the apparent gap between the two notations.

Reading a negative American odd as a loss. −200 announces no loss whatsoever: it is the notation for a favourite. The larger the negative number in absolute value, the more likely the price considers the outcome to be.

Believing one format is “better”. No format gives a higher odd than another. An operator displaying +150 and an operator displaying 2.50 are offering the same price. Comparing two bookmakers means converting into a common unit — and, for a serious comparison, removing each one's margin, as explained on margin-free odds.

Dig into the market

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