How To Read Betting Odds

Odds look like three different systems and are really one number written three ways. Learning to move between them takes ten minutes and removes an entire category of expensive mistake.

American Odds

The default in the United States. A price is either negative or positive, and the sign tells you which side of 100 you are on.

Negative means favourite: the number is what you must risk to win 100. -140 means risk 140 to win 100, returning 240 total.

Positive means underdog: the number is what you win by risking 100. +180 means risk 100 to win 180, returning 280 total.

The reference amount of 100 is a convention, not a requirement. -140 works identically at any stake: risking 14 wins 10, risking 70 wins 50.

A price of exactly +100 or -100 is an even bet, sometimes written as "even" or "pk". Both mean you double your money on a win.

Decimal Odds

Standard in Europe, Australia and most betting exchanges, and considerably easier to work with arithmetically.

A decimal price is the total return per unit staked, including your stake. A price of 2.40 means a 10 stake returns 24 in total: 14 profit plus the original 10.

The conversions:

To convert American to decimal: for a positive price, divide by 100 and add 1. For a negative price, divide 100 by the absolute value and add 1. Decimal odds are worth learning even if you bet exclusively in American format, because comparing 1.91 with 1.95 is far easier than comparing -110 with -105.

Fractional Odds

Traditional in British and Irish racing. A fraction expresses profit over stake: 5/2 means a 2 stake wins 5 in profit, returning 7 total.

Fractions where the first number is smaller than the second, like 1/2, indicate a favourite. Some fractions are written in unfamiliar denominators — 10/11 is simply -110 in American terms — which is why the format has largely lost out to decimal for anything other than racing.

You will encounter fractional odds mostly in international markets and occasionally in futures pricing. Converting to decimal first, then comparing, avoids errors.

Reading A Sportsbook Screen Without Getting Caught

Three things trip people up regularly.

The spread and the price are separate numbers. A line shown as "-6.5 (-115)" means the team must win by seven or more, and you are risking 115 to win 100 for that privilege. Both numbers matter, and books sometimes move the price rather than the spread.

Totals are shown the same way. "o47.5 (-105)" is the over at a slightly better than standard price.

Displayed payouts include the stake. A bet slip showing "to return 240" on a 100 stake means 140 profit, not 240 profit. Books differ in whether they display return or profit, which causes more confusion than any other interface detail.

Why The Two Sides Never Add To 100%

Convert both sides of any market to implied probability and the total will exceed 100%. On a standard -110 spread, each side implies 52.4%, totalling 104.8%. That 4.8% excess is the book's margin.

This is the most important consequence of learning to read odds: the prices are not the book's honest probability estimate, they are that estimate with a margin added. Removing the margin to see what the market actually thinks is a routine calculation, covered in implied probability and vig and juice.

Frequently Asked Questions