2. Odds formats

Decimal, fractional (UK), American format

The world’s three big betting cultures describe the same price in three different ways. The good news: all three answer the same question (how much does the bet pay?), only their reference point differs. Once you understand their logic, conversion is just arithmetic, which we lock in with formulas and practice exercises in subchapter 2.3.

The decimal (European) format is the multiplier of the total payout: stake × odds = payout, stake included. €100 at 2.50 pays €250, of which €150 is profit. You already know it from chapter 1: it is the most transparent format, which is why the course and the platform use it throughout. Lock in two of its properties: it can never go below 1.00, and the larger the number, the smaller the chance it prices.

The fractional (UK) format is the heritage of British racecourses and gives the pure profit relative to the stake: 5/1 says that for every unit staked you win five units of profit, and 6/4 says that four units of stake bring one and a half units. It does not include the stake, so its decimal counterpart is always one greater: 5/1 = 6.00, 6/4 = 2.50, 1/2 = 1.50. A fraction smaller than 1 (odds-on, for example 1/2) always signals a heavy favourite.

The American (moneyline) format relates everything to 100 and works with a sign. The positive number tells you how much profit you get on a 100-unit stake: at +150, a 100 stake brings 150. The negative number tells you how much you must risk for 100 units of profit: at -200, you need a 200 stake for 100 of profit. The dividing line is +100 (2.00 in decimal): above it the outcome is more of an underdog, below it a favourite. The same price at a few familiar levels, in three languages:

• 1Strong favourite: 1.50 decimal = 1/2 fractional = -200 American. €100 stake → €50 profit.
• 2Even money: 2.00 = 1/1 (evens) = +100. €100 stake → €100 profit.
• 3Slight underdog: 2.50 = 6/4 = +150. €100 stake → €150 profit.
• 4Big outsider: 6.00 = 5/1 = +500. €100 stake → €500 profit.

Whatever format you meet, first translate it to decimal — that is the common language. And remember the lesson of chapter 3 in advance: the odds are not really about money but about probability; the format is just packaging.

Exotic formats: Hong Kong, Malay, Indonesian

The Asian betting markets use their own formats, and you can meet them not only at exotic bookmakers: odds comparison sites and Asian handicap markets (chapter 6) often write prices this way too. All three formats relate to a 1-unit stake; the only difference is what they take as the reference point and when they change sign.

The Hong Kong format is the simplest: the pure profit on a 1-unit stake, that is exactly the decimal odds minus 1. 2.50 in Hong Kong is 1.50, and 1.50 is 0.50. It is the decimal cousin of the fractional format: always positive, with no trick in it.

The Malay format always moves between -1 and +1. The positive number is the favourite side’s language: it says how much the profit is on a 1-unit stake (+0.50 = 1.50 decimal). As soon as the profit would exceed the stake (above 2.00 decimal), the number turns negative, and from then on it says how much you must risk for 1 unit of profit: -0.50 means half a unit of stake brings one unit, which is 3.00 in decimal.

The Indonesian format is the scaled-down copy of the American: the same numbers divided by a hundred. The negative number is the favourite’s (-2.00 says you must risk two units for one unit of profit, 1.50 in decimal), the positive is the underdog’s (+1.50 is one and a half units of profit on a 1-unit stake, 2.50 in decimal). The same price at all four levels you already saw in the previous section:

• 1Decimal 1.50: Hong Kong 0.50, Malay +0.50, Indonesian -2.00.
• 2Decimal 2.00 (even money): 1.00 in all three formats.
• 3Decimal 2.50: Hong Kong 1.50, Malay approx. -0.67, Indonesian +1.50.
• 4Decimal 3.00: Hong Kong 2.00, Malay -0.50, Indonesian +2.00.

A quick recognition rule for negative numbers: a value between -1 and 0 can only be Malay; a value below -1 is Indonesian (or American on the scale of hundreds). The trap is that the Malay and Indonesian minus signs mean different things, so with an Asian price always check which format you are looking at and convert to decimal.

Conversion with formulas

Every conversion runs through decimal: whatever you see, you first translate to decimal, and if needed onward to the target format. In the formulas d is the decimal odds, and every other format is denoted by its own letter:

• 1Fractional (a/b): d = 1 + a/b. Going back, you write the value d − 1 as a fraction: 2.75 → 1.75 → 7/4.
• 2American (A): for positive, d = 1 + A/100; for negative, d = 1 + 100/|A|. Going back: if d is at least 2.00, then A = +100 × (d − 1); if smaller, then A = -100 / (d − 1).
• 3Hong Kong (HK): d = HK + 1, going back HK = d − 1.
• 4Malay (M): for positive d = M + 1, for negative d = 1 + 1/|M|.
• 5Indonesian (I): for positive d = I + 1, for negative d = 1 + 1/|I|.

Notice that Malay and Indonesian use exactly the same two formulas, just mirrored. What is the positive (favourite) branch for Malay is the underdog’s for Indonesian, and vice versa. That is precisely why it is dangerous to mix them up: the same number can mean two very different prices.

Practice exercises: first calculate in your head or on paper, only then check the solution.

• 17/4 fractional to decimal. Solution: 1 + 7/4 = 2.75.
• 2-125 American to decimal. Solution: 1 + 100/125 = 1.80.
• 33.40 decimal to American. Solution: above 2.00 it is positive, +100 × 2.40 = +240.
• 4Malay -0.40 to decimal. Solution: 1 + 1/0.40 = 3.50.
• 5Indonesian -2.50 to decimal. Solution: 1 + 1/2.50 = 1.40.
• 61.25 decimal in all the other formats. Solution: fractional 1/4, American -400, Hong Kong 0.25, Malay +0.25, Indonesian -4.00.

The calculation questions of the end-of-chapter test draw new values on every attempt: it is worth repeating until you switch between the formats without thinking. The next chapter brings the real point: the probability hidden behind the odds.