Decimal, fractional and American odds converter
Choose the starting format, type the odds and get the other two, along with their implied probability.
The three odds formats
The same price can be written in three ways. The notation changes, not the price.
- Decimal (2.50). Standard in Spain and most of Europe. It shows what you collect per euro staked, including the euro itself.
- Fractional (3/2). Traditional in the UK and Ireland. It shows profit relative to the stake: you win 3 for every 2 staked.
- American (+150 / -200). Common in the United States. A plus sign shows what you win staking 100; a minus sign shows what you must stake to win 100.
The formulas
Fractional to decimal: numerator ÷ denominator + 1
Positive American to decimal: American ÷ 100 + 1
Negative American to decimal: 100 ÷ |American| + 1
Decimal to American:
- If the odds are 2.00 or more: (decimal − 1) × 100, with a + sign
- If they are below 2.00: 100 ÷ (decimal − 1), with a − sign
Examples
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.50 | 1/2 | -200 | 66.67% |
| 1.91 | 10/11 | -110 | 52.36% |
| 2.00 | 1/1 | +100 | 50.00% |
| 2.50 | 3/2 | +150 | 40.00% |
| 4.00 | 3/1 | +300 | 25.00% |
Check with 2.50 and a €10 stake: in decimal you collect €25 in total. At fractional 3/2 you win €15 plus your €10 stake, also €25. At American +150 you win 150 per 100, that is €15 on €10, again €25.
Why conversions are not always exact
The fractional format uses round numbers, so many decimal prices have no exact fraction. Odds of 1.91 are usually written as 10/11, which is really 1.909. That is why the converter looks for the simplest fraction that rounds to the same decimal price, just as bookmakers do. American odds are also rounded to a whole number. The difference is tiny on one bet, though it can show up over many: if you keep records, always store the decimal price.
Common mistakes
- Forgetting the “+1” when going from fractional to decimal. 3/2 is not odds of 1.50 but 2.50.
- Ignoring the American sign. -150 and +150 are very different prices: 1.67 and 2.50.
- Confusing profit with return. Decimal odds include the return of your stake. Fractional and American do not.
- Comparing formats by eye. Before comparing prices, put them all in the same format.
With the odds in decimal you can work out their implied probability and the bookmaker margin or the payout of a parlay. To find out whether your prices really give you an edge, what matters is your history: see how to measure your yield.
Frequently asked questions
What do -110 odds mean?
That you have to stake 110 to win 100. In decimal it equals 1.91, and it is a very common price on two-outcome markets.
How do I convert 5/2 to decimal?
Divide and add one: 5 ÷ 2 + 1 = 3.50.
Which format should I use?
Decimal is the easiest for calculations, because you only need to multiply and divide. It is the one used by all our calculators and by BetTracker Pro.
Does changing format change what I collect?
No. It is the same price written differently, apart from small rounding differences.