Odds Converter and Implied Probability Calculator
Free odds converter and implied probability calculator: convert American, decimal, multiplier and fractional odds instantly, with formulas and worked examples.
An odds converter translates a betting price between formats: American odds (+135, −110), decimal odds (2.35), a payout multiplier (2.35×), fractional odds (27/20) and implied probability (42.55%). All five describe the same price. Type a number into any box and the others update instantly, so you can compare a US sportsbook, a European book and a pick'em app on the same scale, or see the break-even win rate behind any line.
Odds converter
Type odds in any box and the others fill in.
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Enter your numbers to see results.
The converter is prefilled with an illustrative MLB price: the Mets at +135. Whatever you enter is saved in your browser only.
How to use the odds converter
- Type a price in whichever format you have. American odds need a sign for favourites (
-180); a plain number like135is read as +135. Decimal odds use a dot (2.35), fractional uses a slash (27/20), and the multiplier is the decimal number shown with an × (2.35×). - Read across. Every other box fills in from your input.
- Use implied probability for decisions. It's the format that tells you how often the bet has to win to break even, which is what you compare with your own estimate or a fair line.
- Going the other way works too. Type
60into implied probability to see that a fair 60% favourite is −150 (decimal 1.667).
How odds conversion works
Every format is a different way of writing one number: the total return per $1 staked, which is the decimal odds d.
| From | To decimal d |
|---|---|
| American +A (A ≥ 100) | d = 1 + A/100 |
| American −A (A ≥ 100) | d = 1 + 100/A |
| Multiplier m× | d = m |
| Fractional a/b | d = 1 + a/b |
| Implied probability q | d = 1/q |
And back from decimal:
- Implied probability = 1/d
- American: if d ≥ 2, +(d − 1) × 100; if d < 2, −100/(d − 1)
- Fractional = (d − 1) as a fraction, e.g. d = 2.35 gives 1.35 = 27/20
- Multiplier = d, shown as d×
American odds between −100 and +100 don't exist: +100 and −100 are both even money (decimal 2.00, 50%). Converting to American is usually rounded to a whole number, so decimal 1.91 shows as −110 even though the exact value is −109.89.
Worked example: one price, five formats
Illustrative prices, computed with the formulas above:
| American | Decimal | Multiplier | Fractional | Implied probability | Profit on $100 |
|---|---|---|---|---|---|
| +135 (Mets) | 2.350 | 2.35× | 27/20 | 42.55% | $135.00 |
| −110 (NFL spread) | 1.909 | 1.91× | 10/11 | 52.38% | $90.91 |
| −180 (Lakers ML) | 1.556 | 1.56× | 5/9 | 64.29% | $55.56 |
| +250 (Oilers ML) | 3.500 | 3.50× | 5/2 | 28.57% | $250.00 |
| +100 (pick'em) | 2.000 | 2.00× | 1/1 | 50.00% | $100.00 |
Take the Mets at +135. Decimal = 1 + 135/100 = 2.35, so $1 returns $2.35 (a 2.35× multiplier) and a $100 bet profits $135. Implied probability = 1/2.35 = 42.55%: the Mets must win more than 42.55% of the time for +135 to be a good bet.
Worked example: the win rate a multiplier requires
Pick'em and DFS-style apps often quote payouts as multipliers. Say an app pays 3× on a two-pick entry that needs both picks to hit. Decimal 3.00 implies 33.33% for the entry. If the two picks are independent and equally likely, each must hit √(1/3) = 57.74% of the time to break even, which is like laying about −137 on each leg. Converting the multiplier makes that hidden price visible. (Payout tables and rules vary by app and by state, so always check the actual terms.)
Common odds-conversion mistakes
- Treating implied probability as the true probability. A price's implied probability includes the bookmaker's margin. Two sides at −110 add up to 104.76%; the fair probabilities sum to 100%. Use the no-vig calculator to remove the margin and the vig calculator to measure it.
- Mixing up return and profit. Decimal odds and multipliers include your stake; fractional and American odds describe profit. 2.35 returns $2.35 per $1, while 27/20 means $27 profit per $20 staked.
- Dropping the minus sign. −150 and +150 are very different bets (60% vs 40% implied).
- Rounding too early. −110 is 1.9091, not 1.91. Small rounding errors add up when you multiply parlay legs or compute EV on thin edges.
- Comparing prices across formats by eye. 1.95 decimal, −105 American and 20/21 fractional are almost the same price. Convert first, then compare.
How OddScouter handles odds formats
You rarely need to convert by hand inside OddScouter. Every sportsbook price on the +EV board sits next to the devigged fair odds from a sharp market, with the EV already worked out, so you see at a glance which book's number beats the fair line. The implied probability guide explains why that comparison, not the raw odds, is what matters.
Learn the math behind this calculator
- Implied probability in betting: what a price's implied probability means and how sharps use it.
- How to devig odds: removing the vig for fair probabilities.
- Value betting: how to find positive EV bets: comparing a price with the fair line.
- Parlay EV: multiplying odds and probabilities across legs.
Next steps: turn a price and a fair probability into expected value with the betting EV calculator, or size the bet with the Kelly criterion calculator.
Responsible gambling
Converting odds helps you understand a price; it doesn't make a bet more likely to win. Sportsbooks build a margin into every line, and no tool or method guarantees a profit. Only bet what you can afford to lose. You must be 21+ (or the legal age where you live). If gambling stops being fun, call or text 1-800-GAMBLER for free, confidential help.
Frequently asked questions
How do you convert American odds to decimal?
For positive odds, decimal = 1 + American/100, so +135 becomes 2.35. For negative odds, decimal = 1 + 100/|American|, so −180 becomes 1.556. Decimal odds include your stake: a $10 bet at 2.35 returns $23.50 in total.
How do you convert decimal odds to American odds?
If the decimal odds are 2.00 or more, American = +(decimal − 1) × 100, so 2.50 is +150. Below 2.00, American = −100 ÷ (decimal − 1), so 1.75 is −133. Converters usually round to a whole number.
What does a 2.5x multiplier mean in betting?
A 2.5× multiplier means every $1 staked returns $2.50 in total if the bet wins, which is $1.50 of profit. It is the same number as decimal odds of 2.50, American odds of +150 and fractional odds of 3/2, with a 40% implied probability.
What is −110 in decimal and fractional odds?
−110 is 1.909 in decimal odds and 10/11 in fractional odds. You risk $110 to win $100, and the implied probability is 52.38%, which is why a standard −110 bettor must win more than 52.4% of bets to profit.
What is the difference between decimal and fractional odds?
Decimal odds show the total return per $1, stake included; fractional odds show only the profit relative to the stake. Decimal 3.50 and fractional 5/2 are the same price: a $10 bet returns $35, which is $25 profit.
Related tools: Betting EV Calculator: Expected Value of Any Bet, Vig Calculator: Juice, Hold and Overround of Any Bet.
OddScouter is an information tool, not a sportsbook, and nothing here is betting or financial advice. Positive expected value is not a promise of profit. You must be 21 or older. Gambling problem? Call 1-800-GAMBLER. Responsible gambling resources.
