Odds Converter
American · Decimal · Fractional · Implied %
Convert between any odds format instantly. Enter both sides of a market to see the true vig-free probability — the market's real assessment stripped of the bookmaker's margin.
Enter odds to convert
Favourite: −100 or lower. Underdog: +100 or higher. American odds must be −100 or lower, or +100 or higher. (Note: −100 is treated as +100 / evens).
Enter a valid American odds value: −100 or lower (favourite) or +100 or higher (underdog).
Opposite side of market optional
Enter the odds for the other side of this market (any format). Required to calculate vig-free probability. Example: if you entered −110 above, enter −110 here for a standard spread.
Could not parse the opposite side odds. Enter American (e.g. −110, +150), Decimal (e.g. 1.91), or Fractional (e.g. 10/11).
Common odds — click to load and convert
Converted odds
Enter odds above and click “Convert odds”,
or click a preset to load a common line.
Quick reference
Common odds conversion table
The most frequently encountered odds across US and international markets, with all formats and the break-even win rate for each.
| American | Decimal | Fractional | Implied prob. | Break-even win rate | Net per $100 staked |
|---|---|---|---|---|---|
| +300 | 4.000 | 3/1 | 25.00% | 25.00% | +$300.00 |
| +200 | 3.000 | 2/1 | 33.33% | 33.33% | +$200.00 |
| +150 | 2.500 | 3/2 | 40.00% | 40.00% | +$150.00 |
| +120 | 2.200 | 6/5 | 45.45% | 45.45% | +$120.00 |
| +110 | 2.100 | 11/10 | 47.62% | 47.62% | +$110.00 |
| +100 | 2.000 | 1/1 | 50.00% | 50.00% | +$100.00 |
| −105 | 1.952 | 20/21 | 51.22% | 51.22% | +$95.24 |
| −110 | 1.909 | 10/11 | 52.38% | 52.38% | +$90.91 |
| −115 | 1.870 | 20/23 | 53.49% | 53.49% | +$86.96 |
| −120 | 1.833 | 5/6 | 54.55% | 54.55% | +$83.33 |
| −130 | 1.769 | 10/13 | 56.52% | 56.52% | +$76.92 |
| −150 | 1.667 | 2/3 | 60.00% | 60.00% | +$66.67 |
| −200 | 1.500 | 1/2 | 66.67% | 66.67% | +$50.00 |
| −300 | 1.333 | 1/3 | 75.00% | 75.00% | +$33.33 |
−110 standard line: edge by win rate
The most common odds in US spread and totals markets. Break-even is 52.38%. Winning 50% of bets at −110 is a losing strategy.
| Win rate | Break-even | Edge | EV per $110 staked | Over 100 bets |
|---|---|---|---|---|
| 48% | 52.38% | −4.38pp −EV | −$8.80 | −$880 expected |
| 50% | 52.38% | −2.38pp −EV | −$4.77 | −$477 expected |
| 52% | 52.38% | −0.38pp −EV | −$0.76 | −$76 expected |
| 52.38% | 52.38% | 0.00pp — Break-even | $0.00 | $0 expected |
| 54% | 52.38% | +1.62pp +EV | +$3.25 | +$325 expected |
| 56% | 52.38% | +3.62pp +EV | +$7.25 | +$725 expected |
| 58% | 52.38% | +5.62pp +EV | +$11.27 | +$1,127 expected |
How odds formats work
Understanding the three formats — and why vig matters
American odds
American odds express profit relative to a $100 reference. A negative number (−110) means you risk that amount to win $100. A positive number (+150) means a $100 stake wins that amount.
Converting to decimal: for negatives, 100/|A| + 1. For positives, A/100 + 1. American odds of −100 and +100 both equal 2.000 decimal — they are the same price expressed differently. Values between −99 and +99 are not valid American odds.
Decimal odds
Decimal odds are the total return per unit staked including the stake returned. Odds of 1.909 on a $100 bet return $190.90 total ($90.90 profit + $100 stake). Evens is 2.000, not 1.000. Decimal odds must always be greater than 1.000.
Fractional odds
Fractional odds express profit as a fraction of the stake. 10/11 means win $10 for every $11 staked (profit only, stake not included). Evens is 1/1. Converting to decimal: (numerator / denominator) + 1. Both numerator and denominator must be positive non-zero numbers.
Vig-free probability: why one side isn't enough
A single set of odds tells you the bookmaker's implied probability — which includes their margin. To get the vig-free (true market) probability, you need both sides.
Method: convert both sides to implied probability, sum them. That sum above 100% is the overround. Divide each side's implied probability by the total to get the vig-free split.
Example: standard −110/−110 spread.
Each side: 1/1.909 = 52.38%
Total: 52.38 + 52.38 = 104.76%
Overround: 4.76% (the vig)
Vig-free each side: 52.38 / 104.76 = 50.0%
This tool requires both sides to calculate vig-free probability rather than making an undisclosed symmetric-market assumption.
Conversion formulas
American (neg) → Decimal: 100 / |A| + 1
American (pos) → Decimal: A / 100 + 1
Decimal → Implied: 1 / D × 100%
Decimal → American (D < 2): -(100/(D-1))
Decimal → American (D ≥ 2): (D-1) × 100
Fractional n/d → Decimal: n/d + 1
Vig-free: each side / sum of both sidesAll conversions are mathematically exact. Displayed values are rounded to 3 decimal places for readability.
FAQ
Frequently asked questions
How do you convert American odds to decimal?
For negative American odds: divide 100 by the absolute value, then add 1. Example: −110 gives 100/110 + 1 = 1.909. For positive American odds: divide the odds by 100, then add 1. Example: +150 gives 150/100 + 1 = 2.500. Decimal odds always include the stake returned, so evens is 2.000, not 1.000. Values between −99 and +99 are not valid American odds.
What is the implied probability of −110 odds?
The implied probability of −110 is 52.38%. This is the break-even win rate — the minimum win percentage needed just to break even at those odds. Winning 50% of bets at −110 produces a loss of approximately 4.5% of stakes, not break-even. A standard −110/−110 spread market has a total implied probability of 104.76%, meaning the bookmaker's margin (vig) is 4.76%.
What is the difference between implied probability and vig-free probability?
Implied probability is calculated directly from the offered odds (1 divided by decimal odds) and includes the bookmaker's margin. Vig-free probability strips that margin by dividing each side's implied probability by the sum of both sides. For a −110/−110 market: both sides have 52.38% implied probability summing to 104.76%. Vig-free for each side is 52.38% divided by 104.76% = 50.0%. This requires both sides of the market, which is why this converter asks for the opposite side to compute vig-free probability accurately.
How do you convert fractional odds to decimal?
Divide the numerator by the denominator, then add 1. Example: 5/2 gives 5/2 + 1 = 3.500. Example: 10/11 gives 10/11 + 1 = 1.909. The +1 accounts for the stake returned on a win. Both the numerator and denominator must be positive non-zero numbers — values like 0/5 or 5/0 are not valid fractional odds.
What does +100 or even money mean in American odds?
+100 means a $100 stake wins $100 profit — you double your money on a win. This is evens or even money, equivalent to 2.000 decimal or 1/1 fractional, and implies a 50% break-even win rate. Note that −100 and +100 represent the same price in American odds — both equal 2.000 decimal. If both sides of a market are quoted at +100, there is no visible vig, which is unusual outside promotional offers.
Why does this converter ask for both sides of the market?
Vig-free probability cannot be calculated from a single set of odds alone — you need the full market to know the overround. Some converters show "vig-free probability" based on an undisclosed symmetric-market assumption, which is only accurate when both sides happen to be the same price. This tool requires both sides and shows the overround explicitly, so the vig-free result is always mathematically verifiable. For a single-odds input, the tool shows implied probability clearly labelled as the bookmaker's quoted probability including margin.
Know the break-even rate. Now find the edge.
Converting odds tells you the break-even win rate. Determining whether a bet actually has positive expected value requires an independent probability estimate to compare against it. ZCode System generates AI-driven probability scores across NFL, NBA, MLB, NHL, and soccer — the inputs that turn a break-even rate into an EV calculation.
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