Guide · 6 min read
Odds formats explained: decimal, fractional and American odds, and how to convert them
+150, 6/4 and 2.50 are the same price written three ways. This guide explains each format, gives the conversion formulas and a full table, lists the mistakes that most often cost money when converting, and shows which formats the ArbVantage app can display.
Updated 22 October 2026
Contents
Decimal odds (Europe)
Decimal odds are the total return per 1 unit staked, stake included. At 2.50 a €10 stake returns €25, of which €15 is profit. Bookmakers in Austria such as Tipico, bet365, bwin, Admiral, Interwetten, tipp3 and bet-at-home show decimal odds by default, as do Slovak bookmakers such as Tipsport, Fortuna and Niké.
Decimal odds are the easiest to calculate with: return = stake × odds, and implied probability = 1 / odds. That is why the sure-bet formula uses them too. The core terms are explained in betting basics.
Fractional odds (UK and Ireland)
Fractional odds show only the net profit relative to the stake. 6/4 ("six to four") means: stake 4, win 6, and get your stake back as well.
- 6/4 = 1.5 profit per 1 staked → decimal 2.50
- 1/1 ("evens") → decimal 2.00
- 1/4 ("four to one on") → decimal 1.25
- 10/11 → decimal 1.909, the classic 1.91
British bookmakers use a fixed ladder of common fractions, so some decimal prices can only be written approximately as a fraction.
American odds (+150 / −200)
US sportsbooks show "moneyline" odds with a sign, always relative to 100:
- Plus (+150): the profit you get for a 100 stake. +150 = 150 profit on 100 → decimal 2.50.
- Minus (−200): what you must stake to win 100. −200 = stake 200 to win 100 → decimal 1.50.
−110 is the standard price on both sides of a point spread: stake 110 to win 100 → decimal 1.909. On both sides that gives a payout rate of 95.5%, so a margin of about 4.5%; see bookmaker margin and overround. +100 and −100 both mean decimal 2.00.
Asian formats: Hong Kong, Malay, Indonesian
- Hong Kong odds: the net profit per 1 staked, so decimal − 1. 2.50 → 1.50.
- Malay odds: equal to Hong Kong odds up to 1.00; above that, negative as −1 / Hong Kong. 2.50 → −1 / 1.50 = −0.67. A negative Malay price means: stake this much to win 1.
- Indonesian odds: like American odds divided by 100. 2.50 → +1.50; 1.50 → −2.00.
You mostly meet these formats at Asian bookmakers and on Asian handicap markets. For betting in Austria and Slovakia they hardly matter.
Conversion table
| Decimal | Fractional | American | Hong Kong | Malay | Indonesian | Implied |
|---|---|---|---|---|---|---|
| 1.25 | 1/4 | −400 | 0.25 | 0.25 | −4.00 | 80.0% |
| 1.50 | 1/2 | −200 | 0.50 | 0.50 | −2.00 | 66.7% |
| 1.91 | 10/11 | −110 | 0.91 | 0.91 | −1.10 | 52.4% |
| 2.00 | 1/1 | +100 | 1.00 | 1.00 | +1.00 | 50.0% |
| 2.50 | 6/4 | +150 | 1.50 | −0.67 | +1.50 | 40.0% |
| 3.00 | 2/1 | +200 | 2.00 | −0.50 | +2.00 | 33.3% |
| 5.00 | 4/1 | +400 | 4.00 | −0.25 | +4.00 | 20.0% |
1.91 is rounded; −110 and 10/11 correspond exactly to decimal 1.9091.
Conversion formulas
Fractional: D − 1 as a fraction (2.50 → 1.5 → 3/2, usually written 6/4)
American if D ≥ 2.00: +(D − 1) × 100
American if D < 2.00: −100 / (D − 1)
Hong Kong: D − 1
From fractional a/b: 1 + a / b
From American +X: 1 + X / 100. Example +150 → 2.50
From American −X: 1 + 100 / X. Example −200 → 1.50; −110 → 1.909
From Hong Kong H: H + 1
On precision: no format is more accurate in itself; rounding is what matters. Decimal odds with two decimals round by up to 0.005. Whole-number American odds are very fine for favourites (−110 vs −111) but coarse at long prices. Fractional odds are the coarsest, because only certain fractions are in use. For sure bets with a 1% to 2% margin, even the third decimal place can count.
Common conversion mistakes
- Reading a fraction as a decimal: 6/4 is not 6.4 but 2.50. Fractional odds exclude the stake; decimal odds include it.
- Missing the sign: +200 is decimal 3.00, while −200 is 1.50. A forgotten minus doubles the return you expect.
- Reading Hong Kong odds as decimal: Hong Kong 0.91 is decimal 1.91, not a price below 1.
- Rounding too early: putting −110 into a sure-bet calculation as 1.91 instead of 1.9091 shifts the stakes slightly. With a 1% margin that can make the difference.
- Forgetting deductions: if a bookmaker in Austria passes on the 5% betting fee, use the net price in every format: 2.50 becomes 2.375, so +137.5 rather than +150.
What ArbVantage shows
ArbVantage always calculates internally with decimal odds. It displays them in the format you choose in Settings: decimal, American or fractional. The default is decimal; anyone who picks the USA as their country at sign-up sees American odds first. You can switch at any time, and the app's calculator understands odds typed in any of the three formats. Hong Kong, Malay and Indonesian odds are not displayed.
When placing a bet, always enter the price the bookmaker actually shows. If it differs, the app recalculates the stakes. How a sure bet is built from those prices is explained in sure betting explained.
FAQ
What does −110 mean?
You have to stake 110 to win 100. That equals decimal odds of 1.909 and an implied probability of 52.4%. −110 on both sides of a market gives a margin of about 4.5%.
Which odds format is more accurate?
None in principle. It depends on rounding: decimal odds with two decimals are usually fine enough, American odds are very fine for favourites and coarse at long prices, and fractional odds are the coarsest.
Can I change the odds format in the app?
Yes. In Settings you choose between decimal, American and fractional. ArbVantage always calculates with decimal odds internally, and the display follows your choice.
How do I convert +150 into decimal odds?
For positive American odds calculate 1 + X / 100. +150 gives 1 + 1.5 = 2.50. That equals the fractional price 6/4.
What does evens mean in betting?
Evens is the British name for the fractional price 1/1. You win as much as you stake. In decimal that is 2.00, in American odds +100, and the implied probability is 50%.
Sources
- Steven D. Levitt: Why are gambling markets organised so differently from financial markets? The Economic Journal 114 (2004), on American odds and −110 markets
- Edward O. Thorp: The Kelly Criterion in Blackjack, Sports Betting, and the Stock Market
- Unternehmensserviceportal (USP), Austria: Wettgebührenabrechnung
As of October 2026. Conversions by ArbVantage, identical to the conversion in the app, rounded.
Betting carries risk, sure bets included: odds change, bets get voided and accounts get limited. Only stake money you can afford to lose. Our responsible gambling page lists free, confidential help in Austria and Germany.
Not betting, legal or tax advice. 18+. As of October 2026.