Reading odds and working out returns

Decimal, fractional and American odds all describe the same thing in three different formats. Here is how to read each one, and how to work out what a price is really telling you.

Decimal odds, the default here

Decimal is the format almost every operator on this list uses by default. The number is your total return per unit staked, stake included. A price of 2.50 returns 25 dollars on a 10 dollar stake: 15 dollars profit plus your 10 back.

The arithmetic is simply stake multiplied by odds. That is the whole formula, which is why decimal is the easiest format to work with.

Fractional odds

Common in the UK. The fraction gives profit relative to stake, excluding the stake itself. 3/2 means three units profit for every two staked, so a 10 dollar stake returns 25 dollars in total. To convert to decimal, divide the fraction and add one: 3 divided by 2 is 1.5, plus 1 makes 2.50.

American odds

Written with a plus or minus. Plus 150 means a 100 unit stake profits 150. Minus 150 means you must stake 150 to profit 100. To convert a positive number to decimal, divide by 100 and add 1. For a negative number, divide 100 by the absolute value and add 1.

Implied probability and the margin

Divide 1 by the decimal odds to get the probability the price implies. A price of 2.50 implies 40 percent. This is the useful part: it turns a price into a statement about likelihood that you can agree or disagree with.

Add the implied probabilities of every outcome in a market and the total exceeds 100 percent. The excess is the operator margin. On a two-way market a total of 104 percent means a four percent margin. Deep, competitive markets run tighter margins. Thin markets, including most Somali Premier League fixtures, run much wider ones. That is the real cost of betting a thin market, and it does not appear anywhere on the screen.

Accumulators and why bonus terms use them

Multiply the decimal odds of each leg to get the accumulator price. Four legs at 1.50 gives 1.5 to the fourth power, which is 5.06. The margin compounds with every leg, which is exactly why welcome bonus rollover terms are almost always written as accumulators with a minimum price per selection. The operator is not being generous, it is choosing the market where its edge is largest.

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