How Betting Odds Work: Decimal, Fractional and American Odds Explained
One price, three ways to write it. Decimal, fractional, American and Polymarket odds explained with a real match priced at Toto, Unibet, Polymarket and Overtime.
Last reviewed November 3, 2026
Key takeaways
- >Decimal odds are the total return per unit staked: €10 at 2.90 returns €29.00, of which €19.00 is profit
- >Fractional odds are profit over stake (19/10); American odds are profit on 100 (+190) or the stake needed to win 100 (−303)
- >A Polymarket share price is the implied probability itself: 40¢ = 40% = decimal odds of 2.50
- >Formats are only presentation; which book you take the price from matters far more
- >The implied probabilities of a match add up to more than 100%; the excess is the bookmaker's margin
A betting price is one number written three ways. Decimal odds, fractional odds and American odds all describe exactly the same thing: how much a bet pays back, and with that, how likely the price says the outcome is. Once you can switch between them, every bookmaker in the world reads the same.
We will use one real match throughout: Liverpool vs Arsenal, Premier League, 1 November 2026. These were the last 1X2 prices we recorded at four venues before kickoff (on the morning of the match, or the last change before it):
Venue | Liverpool | Draw | Arsenal |
|---|---|---|---|
Toto | 2.90 | 3.40 | 2.55 |
Unibet | 2.95 | 3.45 | 2.55 |
Polymarket | 2.94 (34¢) | 3.45 (29¢) | 2.50 (40¢) |
Overtime | 2.97 | 3.34 | 2.50 |
Four venues, four slightly different opinions, and two different ways of writing them down. Here is how to read every one of them.
Decimal odds: the return on every euro
Decimal odds are the format Toto, Unibet and Overtime show by default, and the easiest to calculate with. The number is what one unit of stake pays back in total, including the stake itself.
- Return = stake × decimal odds
- Profit = stake × (decimal odds − 1)
€10 on Liverpool at Toto's 2.90 returns €29.00: your €10 back plus €19.00 profit. The same €10 at Unibet's 2.95 would have returned €29.50. Same match, same bet, €0.50 more, just for picking the other book.
Decimal odds can never be below 1.00. A price of 1.00 would mean you only get your own stake back.
Fractional odds: profit against stake
Fractional odds are the traditional British format: profit / stake. "19/10" (said "nineteen to ten") means you win €19 for every €10 you stake, and get the stake back on top.
- Decimal → fractional: subtract 1, then write it as a fraction. 2.90 − 1 = 1.90 = 19/10.
- Fractional → decimal: divide, then add 1. 31/20 = 1.55, + 1 = 2.55.
A few you will see constantly:
Fractional | Decimal | Said as |
|---|---|---|
1/1 | 2.00 | "evens" |
1/2 | 1.50 | "two to one on" |
2/1 | 3.00 | "two to one" |
5/2 | 3.50 | "five to two" |
10/1 | 11.00 | "ten to one" |
American odds: plus and minus around 100
American (moneyline) odds use 100 as the reference point, with a sign that tells you which way round to read it:
- A plus sign (an underdog): the profit on a 100 stake. +190 means a 100 bet wins 190.
- A minus sign (a favourite): what you must stake to win 100. −303 means you stake 303 to win 100.
The conversions:
- Decimal 2.00 or higher → American: (decimal − 1) × 100, with a plus sign. 2.90 → +190.
- Decimal below 2.00 → American: −100 / (decimal − 1). Bayern Munich at home to Dortmund the same weekend was 1.33 at Toto: −100 / 0.33 = −303.
- American → decimal: plus odds: 1 + odds / 100. Minus odds: 1 + 100 / |odds|. The classic US "−110" is 1 + 100/110 = 1.91.
Polymarket: the price is the probability
Polymarket does not quote odds at all. Each outcome is a share that pays $1 if it happens and $0 if it doesn't, and the share price is what the market charges for it. Arsenal at 40¢ means you pay $0.40 for a share that pays $1.00 if Arsenal win.
That makes the conversion the simplest of all:
- Decimal odds = 1 / share price. 1 / 0.40 = 2.50.
- The share price is the implied probability. 40¢ = 40%.
(For the table above we used the price you could actually buy at, the best "ask" in Polymarket's order book, not the midpoint.)
All formats side by side
Toto's prices for Liverpool vs Arsenal, in every format, plus what each price implies about the chance of that outcome:
Outcome | Decimal | Fractional | American | Implied probability |
|---|---|---|---|---|
Liverpool | 2.90 | 19/10 | +190 | 34.5% |
Draw | 3.40 | 12/5 | +240 | 29.4% |
Arsenal | 2.55 | 31/20 | +155 | 39.2% |
Total |
|
|
| 103.1% |
The three formats in the middle columns are pure presentation: they always say the same thing. The last column is where it gets interesting. Implied probability is 1 / decimal odds, and the three outcomes of this match add up to 103.1%, not 100%. Those extra 3.1 percentage points are Toto's margin on this match, the built-in price of betting with a bookmaker. See What is implied probability? for the formula, and The bookmaker's margin for how big that margin is at each book, measured over 600+ games.
Which format should you use?
Use decimal. It is the only format where comparing two prices is a matter of "bigger is better," and the profit is one multiplication away. Fractional and American odds are worth being able to read, because British and American sites, tipsters and TV graphics use them, but converting them to decimal first avoids almost every mistake.
What matters far more than the format is which book you take the price from. In our match, Unibet paid more than Toto on Liverpool and the draw; Overtime paid the most on Liverpool; Toto and Unibet tied on Arsenal. Differences of a few cents per bet look small, but they are applied to every bet you ever place.
Frequently asked questions
Are fractional odds "better" than decimal odds?
No. They are the same price written differently. 19/10 and 2.90 pay exactly the same.
What does "odds-on" mean?
A price below evens (below 2.00 in decimal, below 1/1 in fractional, a minus sign in American): the market rates the outcome as more likely than not, and you win less than you stake.
Why does Polymarket show cents instead of odds?
Because you are buying a share that pays $1 if the outcome happens. The cents price is both the cost and the implied probability; 1 divided by it gives the decimal odds.
Why don't the implied probabilities add up to 100%?
Because a bookmaker builds its margin into every price. The total above 100% is that margin. It is covered in full in The bookmaker's margin.
Prices: the last 1X2 prices recorded by Edge Terminal before kickoff of Liverpool vs Arsenal on 1 November 2026 (Toto, Unibet and Overtime: decimal odds; Polymarket: 1 / best ask). Bayern Munich vs Borussia Dortmund, 31 October 2026, Toto. Snapshot taken 3 November 2026.