Odds look like simple numbers, but they hide a lot: what you win, how likely the bookmaker thinks an outcome is, and how the bookmaker earns money. This guide explains the basics for people who are new to sports betting. It is education only. It gives no tips and does not promise that anyone will win.
What odds are
#Odds are a price. They tell you how much you get back if your bet wins, compared with the amount you put in. They also carry an idea of how likely the bookmaker thinks the outcome is. A low number means the outcome is seen as likely. A high number means it is seen as unlikely.
Odds are not the true chance. The bookmaker builds a margin into them, which we explain below.
Decimal odds
#Decimal odds are the style used in the Balkans and across most of Europe. The number shows the total return per 1 unit staked, including your stake.
- Return = stake x odds
- Profit = return minus stake
Worked examples:
- Stake 10 at odds 2.50: return 10 x 2.50 = 25. Profit = 25 - 10 = 15.
- Stake 20 at odds 1.50: return 20 x 1.50 = 30. Profit = 30 - 20 = 10.
- Stake 5 at odds 4.00: return 5 x 4.00 = 20. Profit = 20 - 5 = 15.
If the bet loses, you lose the stake. Profit is then minus the stake, here minus 10, minus 20 or minus 5.
Fractional and American odds
#You may see other styles on foreign sites, so it helps to recognise them.
Fractional odds (common in the UK and Ireland) show profit compared with the stake.
- 3/1 means you win 3 for every 1 staked. Stake 10 gives profit 30 and return 40. In decimal, that is 4.00.
- 1/2 means you win 1 for every 2 staked. In decimal, that is 1.50. "Evens" (1/1) is 2.00.
American odds (the moneyline, common in the USA) use 100 as the base.
- A plus number, such as +300, is the profit on a stake of 100. It equals 4.00 in decimal.
- A minus number, such as -200, is the stake you need to make a profit of 100. It equals 1.50 in decimal.
Implied probability
#Odds can be turned into a percentage. This is called the implied probability. With decimal odds, divide 1 by the odds.
- Odds 2.00: 1 / 2.00 = 0.50, so 50 percent.
- Odds 2.50: 1 / 2.50 = 0.40, so 40 percent.
- Odds 4.00: 1 / 4.00 = 0.25, so 25 percent.
- Odds 1.25: 1 / 1.25 = 0.80, so 80 percent.
So odds of 2.50 say "about 4 chances in 10". This is the bookmaker's price, not a fact about the match.
The bookmaker margin (overround)
#If the bookmaker paid out at fair odds, it would earn nothing on average. So it shortens the odds a little. This built-in profit is called the margin, the overround or the vigorish ("vig").
A simple example is a tennis match between two players who each have a 50 percent chance. Fair odds would be 2.00 for each. Suppose the bookmaker offers 1.80 on both:
- Implied probability of player A: 1 / 1.80 = 55.6 percent.
- Implied probability of player B: 1 / 1.80 = 55.6 percent.
- Total: 55.6 + 55.6 = 111.1 percent.
A fair market adds up to exactly 100 percent. Here it adds up to 111.1 percent. The extra 11.1 percent is the overround. It is the reason the numbers add up to more than 100.
You can see the effect in money. Say 100 is staked on each player, 200 in all. Whoever wins, the bookmaker pays out 100 x 1.80 = 180 and keeps 20. That is 10 percent of the money taken, whatever the result.
Margins differ between bookmakers, sports and markets. You can work out the margin of any market yourself with the sum above.
What about value?
#You may hear the word "value": a bet where the real chance is higher than the odds suggest. Spotting it is very hard, because you must know the true chance better than the bookmaker does. No method, system or tip service is known to beat the margin over a long time for ordinary players. Treat anyone who promises otherwise with suspicion.
Bet types
#- Single: one selection, one result. Simple to follow. Stake 10 at 2.00 returns 20 if it wins.
- Accumulator (acca, multiple, parlay): several selections in one bet. This is the "listic" (ticket) in the Balkans. The odds are multiplied. For example 1.50 x 2.00 x 1.80 = 5.40. Stake 10 returns 54 and profit is 44. But every selection must win. One loss means the whole bet loses. The more selections, the lower the chance, and the margin is paid on each leg.
- System bet: several selections, split into smaller combined bets, so one loss does not lose everything. For example, "2 from 3" with selections A, B and C makes 3 two-selection bets: AB, AC and BC. With 10 on each, the total stake is 30. It costs more than one acca because you place many bets.
- Live (in-play) betting: you bet while the match is on. Odds change fast. The pace can make it easier to bet more than planned, so many people find it riskier.
- Cash out: a bookmaker may offer to settle an open bet early for an amount it names. If the bet is going well you take a smaller sure return. If it is going badly you save part of the stake. The price includes the bookmaker's margin, and it is not offered on every bet.
Words you will meet
#- Stake: the money you put on the bet.
- Return (or payout): the total money you get back if you win, including the stake.
- Profit: return minus stake. This is what you actually gained.
- Void: the bet is cancelled, for example if a match is called off. The stake is normally given back. In an accumulator, a void selection is usually dropped and the odds are recalculated without it.
Always read the bookmaker's rules for the exact meaning, as they differ.
Common mistakes
#- Reading odds as a promise or a "sure thing". Low odds still lose sometimes.
- Forgetting that the return includes the stake, so profit is smaller than the number you see.
- Building long accumulators for a big return. The chance of all legs winning drops quickly. Three selections that are each about 55 percent likely win together only about 17 percent of the time.
- Chasing losses with bigger stakes.
- Betting live without a plan or a limit.
- Ignoring the margin and thinking small edges are free.
- Betting with money needed for rent, food or bills.
In short
#- Decimal odds: return = stake x odds. Profit = return minus stake.
- Implied probability = 1 divided by the odds.
- The implied probabilities of all outcomes add up to more than 100 percent. The extra is the bookmaker margin.
- No method beats the margin over time, so do not count on winning.
- An accumulator needs every selection to win. A single needs one.
- Check what stake, return, profit and void mean in the rules before you bet.
Play with care
#Gambling is for adults aged 18 and over. It is entertainment, not a way to earn money, and it can be addictive. Play only with money you can afford to lose. Set a deposit limit and a time limit before you start, and stop when you reach them. There is no guarantee of winning, and understanding odds does not change that. If gambling stops being fun, talk to someone you trust. GambleAware offers free, confidential support (it serves Great Britain, so look for a service in your own country). Gambling rules differ by country, so check the law where you live. This guide is general information, not legal advice.
