Fractional odds, along with decimal odds and American odds, are one of the three main ways of expressing the price of a fixed odds wager. They are widely used by Irish and UK-based bookmakers, and offer a relatively straightforward way of understanding the potential return against a staked price for any given market.

As indicated by the name, fractional odds in any given market are expressed as, well, a fraction such as 10/1 or 9/4 (spoken as ten-to-one and nine-to-four respectively). The fraction indicates the amount that will be paid out against a given stake. In these examples, a 10/1 bet will pay 10 times the stake (€10 for a €1 stake, €30 for a €3 stake and so on), along with the return of the initial stake. Odds of 9/4 will pay 9 divided by 4 (2.25) multiplied by the initial stake, as well as the return of the stake itself.

Odds of 1/1 are called evens, and indicate that the amount paid out will be equal to the stake, and once again the stake is also returned.

For odds below this, such as a heavy favourite in a given market – Australia to beat Ireland in a one-day international for example – the fraction is reversed and listed as something like 1/4 (pronounced as either one-to-four, or four-to-one against). The calculation for determining the pay out remains the same: the stake is multiplied by the fraction. For a price of 1/4 the payout would therefore be 0.25 multiplied by the stake – a return of €2.50 for a €10 bet for example, plus of course the initial €10 stake returned.

The table below gives a good indication of the relative prices of some common fractional odds:

In a market for a single overall winner from a list of options, such as the leading run scorer in a cricket tournament or the overall winner of the one-day international World Cup, the fractional odds are generally (though by no means always) listed as something-to-one – 3/1, 5/1, 12/1 and so on. The team viewed as the favourite will have the smallest fraction (e.g. 3/1), whilst a reasonable outside chance could be priced at around 16/1. Rank outsiders may have odds as high as 1000/1.

For markets that have a limited number of outcomes, such as the choice of winner in a specific match, the odds vary much more widely and are expressed using a wider range of fractions. In a game between two closely matched teams, the slight favourite may be priced at 11/8, with the slight outsider at 8/5. By contrast, in a game between two mismatched teams the favourite could be priced at 2/7 and the outsider at 8/1.

Fractional odds in these circumstances can seem a little cumbersome, especially for someone more used to the decimal odds system, but the relative weighting between different odds quickly becomes apparent – even if a calculator can come in handy at times!