American Odds vs Decimal Odds: Converting Between Formats
The same price written three ways. How to convert American odds to decimal and back, why decimal odds make parlay maths trivial, and which format to use for what.
Updated 4 min read
A price is a price. -110, 1.909 and 10/11 describe the same bet, and a sportsbook switching its display setting is not changing what it will pay you. The formats differ in what they make easy.
The three formats side by side
| American | Decimal | Fractional | Implied probability | Profit on $100 |
|---|---|---|---|---|
| -300 | 1.333 | 1/3 | 75.0% | $33.33 |
| -150 | 1.667 | 2/3 | 60.0% | $66.67 |
| -110 | 1.909 | 10/11 | 52.4% | $90.91 |
| +100 | 2.000 | 1/1 | 50.0% | $100.00 |
| +150 | 2.500 | 3/2 | 40.0% | $150.00 |
| +350 | 4.500 | 7/2 | 22.2% | $350.00 |
Three things follow from that table.
Decimal odds are a multiplier for your total return. A $50 bet at 2.50 returns $125. There is no sign to interpret and no separate formula for favourites — the number is simply what each dollar comes back as.
American odds are a multiplier for profit, quoted against $100, with the direction of the quote flipping at even money. That discontinuity at ±100 is what makes them awkward to compare: is -120 further from +105 than +130 is? In decimal, 1.833, 2.05 and 2.30 sort themselves.
Fractional odds are profit as a ratio. 7/2 means seven units of profit for every two risked. Common in horse racing and in UK markets, rare on a North American sportsbook.
Converting American to decimal
Positive odds: decimal = (odds ÷ 100) + 1
+275 becomes (275 ÷ 100) + 1 = 3.75
Negative odds: decimal = (100 ÷ |odds|) + 1
-130 becomes (100 ÷ 130) + 1 = 1.769
The + 1 is your stake coming back. Everything to the left of it is profit per dollar risked.
Converting decimal to American
Which formula you need depends on whether the decimal price is above or below 2.00.
Decimal of 2.00 or greater: american = (decimal − 1) × 100
3.40 becomes (3.40 − 1) × 100 = +240
Decimal below 2.00: american = −100 ÷ (decimal − 1)
1.45 becomes −100 ÷ 0.45 = −222
Why decimal odds win for parlays
This is the practical reason to learn the format even if your sportsbook displays American.
To combine legs in a parlay, you multiply the decimal odds together. That is the entire calculation.
A three-leg parlay at -110, +120 and -150:
- Convert: 1.909, 2.200, 1.667
- Multiply: 1.909 × 2.200 × 1.667 = 7.000
- A $25 bet returns 25 × 7.000 = $175.00, a profit of $150.00
Attempting the same thing in American odds means converting to decimal internally anyway, or compounding profit leg by leg while keeping track of returned stake at each step. People get it wrong, and the error is always in the optimistic direction.
Converting to implied probability
Decimal makes this the simplest of all:
implied probability = 1 ÷ decimal odds
A price of 2.50 implies 1 ÷ 2.50 = 40%. A price of 1.667 implies 60%.
Compare that to the American version, which needs two formulas and a sign check. If you are doing any analysis at all — comparing your estimate of an outcome to the market's, or checking how much margin a sportsbook has built into a line — decimal is the format to work in.
Which format should you use?
Use whichever your sportsbook shows for placing bets — translating in your head at the moment of committing money is how people bet the wrong side.
Switch to decimal when you are:
- Comparing prices across several sportsbooks, where the sorting is instant.
- Calculating a parlay.
- Converting prices to probabilities to check whether you think a line is wrong.
- Reading international sources, which quote decimal by default.
Related reading
- How to read American betting odds — the full breakdown of plus and minus prices.
- How to calculate parlay payouts — the multiplication above, in detail, including why parlays are priced worse than their legs.
- Line shopping: why the best price matters more than the best pick — what a half-point of price is actually worth.
Frequently asked questions
- How do I convert American odds to decimal odds?
- For positive American odds, decimal = (odds ÷ 100) + 1. For negative odds, decimal = (100 ÷ |odds|) + 1. So +150 becomes 2.50 and -150 becomes 1.667.
- Are decimal odds better than American odds?
- Neither is better as a price — they describe the same thing. Decimal odds are easier to compare at a glance and much easier to multiply for parlays, because the decimal figure already includes your returned stake.
- What is -110 in decimal odds?
- -110 equals 1.909 in decimal. A $100 bet returns $190.91 in total: $90.91 profit plus the original $100 stake.
- Do sportsbooks let you change the odds format?
- Most US and Canadian sportsbooks have a display setting that switches between American, decimal and fractional. The underlying price does not change — only how it is written.
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BestSlip Editorial Team
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The BestSlip editorial team writes the explanatory material behind the product: how prices are quoted, how markets are built, and what the arithmetic underneath them says. Everything published here is educational. BestSlip is not a sportsbook and does not accept bets or deposits.
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