Betting odds tell you two things: how much a winning bet pays, and how likely the bookmaker thinks the outcome is. Decimal odds show your total return for every 1 unit staked, fractional odds show your profit relative to your stake, and American odds show either the profit on a 100 stake (plus sign) or the stake needed to win 100 (minus sign). This guide explains each format, how to convert between them and how to turn any price into a probability.
How do betting odds work?
Every price is the bookmaker's estimate of a probability, turned into a payout. The shorter the odds, the more likely the outcome is considered and the less it pays. The longer the odds, the less likely it is considered and the more it pays.
The favourite is the outcome with the shortest odds. When a price pays less than your stake in profit, it is called odds-on (for example 1/2 or 1.50). When it pays more than your stake, it is odds-against (for example 2/1 or 3.00). Evens sits in the middle: you win exactly what you staked.
The format is only presentation. 2/1, 3.00 and +200 all describe exactly the same bet. UK and Irish bookmakers have traditionally used fractional odds, Europe and Australia mostly use decimal, US sportsbooks use American odds, and Canadian sites commonly offer decimal and American. Most betting sites let you switch format in the settings.
Decimal odds explained
Decimal odds are the simplest format. The number shows your total return for each 1 unit staked, and that return already includes your stake.
Total return = stake × decimal odds. Profit = stake × (decimal odds - 1). Anything below 2.00 is odds-on, anything above 2.00 is odds-against, and 2.00 is evens.
Fractional odds explained
Fractional odds show profit relative to stake. The first number is what you win and the second is what you stake to win it. 5/2, said "five to two", means you win 5 for every 2 you stake, and you also get your stake back.
Profit = stake × (first number ÷ second number). Total return = profit + stake. When the first number is smaller, as in 1/2 or 4/6, the bet is odds-on. When it is bigger, as in 2/1 or 5/1, it is odds-against. 1/1 is called evens.
50 to 1 odds, written 50/1, mean you win 50 for every 1 you stake. A £2 bet at 50/1 returns £102: £100 profit plus your £2 stake. The implied chance of a 50/1 shot is 1 in 51, or about 2%.
American odds explained (moneyline odds)
American odds, also called moneyline odds, are built around a 100 stake. A plus sign shows the profit on a 100 stake. A minus sign shows how much you must stake to make 100 profit. +100 and -100 both mean evens.
+250 means a $100 bet wins $250 profit, so $350 back in total. -150 means you must stake $150 to win $100 profit, so $250 back in total. The ratio works for any stake: $30 at -150 wins $20.
To convert American odds to decimal: for plus odds, divide by 100 and add 1, so +250 becomes 3.50. For minus odds, divide 100 by the number without its sign and add 1, so -150 becomes 100 ÷ 150 + 1 = 1.67.
To go the other way, decimal odds of 2.00 or more become (decimal - 1) × 100 with a plus sign, and decimal odds below 2.00 become -100 ÷ (decimal - 1). So 3.00 is +200 and 1.50 is -200.
Odds conversion table
Common prices in all three formats, with the implied probability each one represents. Decimal odds and percentages are rounded.
| Fractional | Decimal | American | Implied probability |
|---|---|---|---|
| 1/5 | 1.20 | -500 | 83.3% |
| 1/3 | 1.33 | -300 | 75.0% |
| 1/2 | 1.50 | -200 | 66.7% |
| 4/6 | 1.67 | -150 | 60.0% |
| 10/11 | 1.91 | -110 | 52.4% |
| Evens (1/1) | 2.00 | +100 | 50.0% |
| 6/4 | 2.50 | +150 | 40.0% |
| 2/1 | 3.00 | +200 | 33.3% |
| 5/2 | 3.50 | +250 | 28.6% |
| 3/1 | 4.00 | +300 | 25.0% |
| 5/1 | 6.00 | +500 | 16.7% |
| 10/1 | 11.00 | +1000 | 9.1% |
| 50/1 | 51.00 | +5000 | 2.0% |
| 100/1 | 101.00 | +10000 | 1.0% |
Implied probability: what the odds really say
Implied probability = 1 ÷ decimal odds, multiplied by 100 for a percentage. Odds of 2.50 imply 1 ÷ 2.50 = 40%. For fractional odds, divide the second number by the sum of both numbers: 6/4 is 4 ÷ 10 = 40%.
Add up the implied probabilities of every outcome in a market and you get more than 100%. The excess is the bookmaker's margin, also called the overround or vig. It is how the bookmaker builds in a profit.
Odds are an estimate, not a fact. A bet only has long-term value when your honest estimate of the probability is higher than the implied probability, and even then any single bet can lose.
Common mistakes when reading odds
Most errors come from mixing up formats or reading too much into a single price.
- Confusing return with profit. Decimal odds include your stake; fractional and American odds show profit only.
- Reading a minus American price as a loss. -200 is simply a short-priced favourite, not a negative payout.
- Treating odds as the true chance. Prices include the margin and reflect the bookmaker's view and where money has been placed.
- Comparing prices in different formats. Convert everything to one format, ideally decimal, before you compare.
Useful calculators
FAQ
What does 50 to 1 mean in betting?
50/1 means you win 50 units of profit for every 1 unit staked, plus your stake back. A £10 bet returns £510. The implied probability is 1 in 51, about 2%.
What does evens mean in betting?
Evens means your profit equals your stake. It is 1/1 in fractional, 2.00 in decimal and +100 in American odds, with an implied probability of 50%.
What does -110 mean in betting?
-110 means you must stake 110 to win 100 profit. It equals decimal odds of about 1.91 and implies a 52.4% chance, which is the win rate you need to break even at that price.
How do I convert American odds to decimal?
For positive odds, divide by 100 and add 1, so +200 becomes 3.00. For negative odds, divide 100 by the number without its minus sign and add 1, so -200 becomes 1.50.
Which odds format is best?
They all describe the same bet, so use whichever you read fastest. Many bettors prefer decimal because returns and implied probabilities are the quickest to calculate.
Do lower odds mean a safer bet?
Lower odds mean the outcome is considered more likely, not certain. Short-priced favourites still lose regularly, and betting always carries risk.
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For information only — betting involves risk and no result is guaranteed. 18+. Disclaimer