American (moneyline) odds to decimal: the conversion formula
For a plus price, decimal = X / 100 + 1, so +250 is 3.50. For a minus price, decimal = 100 / X + 1, so -200 is 1.50. Both give total return per shilling, stake included.
What an American price states
American odds, also called moneyline odds, are written as a number with a plus or minus sign, such as +250 or -150. The sign tells you which question the number answers. A plus price states the profit on a KES 100 stake, and a minus price states the stake needed to make KES 100 of profit.
Decimal odds state the total return per shilling, stake included, as covered in the guide on decimal and fractional odds. Moving from American to decimal is therefore a matter of turning "profit on 100" or "stake for 100 profit" into "return on 1".
The two formulas
Write the American number without its sign as X and the decimal price as D. The formula you use depends only on the sign.
The "+ 1" in both is the returned stake. Without it you would have profit per shilling, which is the fractional form of the same price.
Why the formulas work
Take +250. A KES 100 stake earns KES 250 of profit, so each shilling earns 250 ÷ 100 = 2.50 of profit. Add the shilling back and the return per shilling is 3.50, which is the decimal price.
Take -200. You must stake KES 200 to earn KES 100 of profit, so each shilling earns 100 ÷ 200 = 0.50 of profit. Add the shilling back and the return per shilling is 1.50. The same reasoning holds for any X, which is where the second formula comes from.
Worked examples in shillings
Illustrative example: a plus price
A stake of KES 200 at +250. Decimal: 250 ÷ 100 + 1 = 3.50. Total return if it wins: 200 × 3.50 = KES 700. Profit: 700 − 200 = KES 500. Check against the American price: KES 200 is two lots of KES 100, and each lot earns KES 250, so the profit is KES 500.
Illustrative example: a minus price
A stake of KES 300 at -150. Decimal: 100 ÷ 150 + 1 = 1.6667, shown as 1.67. Total return if it wins: 300 × 1.6667 = KES 500. Profit: KES 200. Check: KES 150 earns KES 100, so KES 300 (two lots of 150) earns KES 200.
If the converted price is rounded to 1.67 before multiplying, 300 × 1.67 = KES 501, which is a rounding difference and not a different price. Keep the unrounded figure when the arithmetic matters.
Converting decimal back to American
The reverse depends on whether the decimal price is at least 2.00. First compute the profit per shilling, which is D − 1.
Decimal 3.40: (3.40 − 1) × 100 = +240. Decimal 1.80: 1.80 − 1 = 0.80, and 100 ÷ 0.80 = 125, so the price is -125. Check it with the first formula: 100 ÷ 125 + 1 = 1.80.
Conversion table
Each row applies the formula above. Implied probability is 1 ÷ D, which for a plus price is 100 ÷ (X + 100) and for a minus price is X ÷ (X + 100). Figures are rounded to two decimal places.
| American | Decimal | Implied probability | Return on KES 100 | Profit on KES 100 |
|---|---|---|---|---|
| +500 | 6.00 | 16.67% | KES 600.00 | KES 500.00 |
| +250 | 3.50 | 28.57% | KES 350.00 | KES 250.00 |
| +200 | 3.00 | 33.33% | KES 300.00 | KES 200.00 |
| +150 | 2.50 | 40.00% | KES 250.00 | KES 150.00 |
| +100 | 2.00 | 50.00% | KES 200.00 | KES 100.00 |
| -110 | 1.91 | 52.38% | KES 190.91 | KES 90.91 |
| -150 | 1.67 | 60.00% | KES 166.67 | KES 66.67 |
| -200 | 1.50 | 66.67% | KES 150.00 | KES 50.00 |
| -400 | 1.25 | 80.00% | KES 125.00 | KES 25.00 |
| -1000 | 1.10 | 90.91% | KES 110.00 | KES 10.00 |
The probability column is read from the price alone. How to interpret it, and why it overstates the true chance, is set out in the guide on converting betting odds to implied probability.
What -110 tells you about the margin
A pair of prices of -110 on each side of a two-way market is common in American-style listings. Each side implies 110 ÷ 210 = 52.38%, and the two together make 52.38% + 52.38% = 104.76%. The 4.76 points above 100% are the built-in margin, which the note on what overround means explains and the guide on calculating the bookmaker's margin sets out in full.
Common slips
- Reading -150 as a loss of KES 150. It means a stake of KES 150 earns KES 100 of profit if the bet wins. A losing bet loses the stake, whatever the price.
- Using X ÷ 100 without adding 1. That gives the profit per shilling, not the decimal price.
- Treating a bigger number as a better price. -400 is a short price and +400 is a long one, and the sign decides everything.
- Mixing the formulas. A minus price needs 100 ÷ X, with 100 on top. Using X ÷ 100 on -200 would give 3.00, which is the price of +200.
- Letting a short price hide the risk. At -1000 a KES 1,000 stake earns only KES 100, while one loss costs the whole KES 1,000. Set limits first, as described in the guide on setting a betting budget and limits.
What the law says about showing odds
Regulation 23(1) of the Gambling Control (Conduct of Gambling Operations) Regulations, 2026 says a licensee shall clearly display betting odds, rules and terms applicable to each bet. It does not name a format, so a reader may meet decimal, fractional or American prices and should convert before comparing.
Betting is for adults aged 18 and over. Gambling is addictive: a conversion changes how a price is written, not what it costs you over time.
Questions and answers
What is the formula for converting American odds to decimal?
For a positive price +X, decimal = X / 100 + 1. For a negative price -X, decimal = 100 / X + 1. For example +150 gives 150 / 100 + 1 = 2.50, and -150 gives 100 / 150 + 1 = 1.67 when rounded to two decimal places.
Is -100 the same as +100?
Yes. Both give decimal odds of 2.00: a KES 100 stake returns KES 200 in total, which is KES 100 of profit. The two signs meet at this point, and an even-money price is usually written +100.
What does the number after the minus sign mean?
It is the stake needed to win KES 100 of profit. At -200 you stake KES 200 to make KES 100 of profit, so a KES 200 bet returns KES 300 in total.
Can decimal odds from an American price ever be below 1.00?
No. Both formulas add 1, which is the returned stake, to a positive number, so the decimal result is always above 1.00. A large minus price such as -1000 gives 1.10.
Does Kenyan law require American odds to be shown in a particular format?
Regulation 23(1) of the Gambling Control (Conduct of Gambling Operations) Regulations, 2026 requires a licensee to clearly display betting odds, rules and terms applicable to each bet. It does not name an odds format.