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Odds to Percentage Calculator
Convert your odds
American odds use a plus sign for the underdog (+150) and a minus sign for the favorite (−200). Decimal odds include your stake; fractional odds show profit per unit staked.
Example: +150 → 40.0% implied probability; −200 → 66.7%; decimal 2.50 → 40.0%; and 40% back again → +150 / 2.50 / 3/2.
Behind the numbers
How odds become a percentage
Odds and probability say the same thing in different forms. American odds, decimal odds and fractional odds are just three ways to write one price, and the implied probability is the chance that price suggests — the break-even point, where a bet neither wins nor loses money over time. Enter odds in any format and this calculator shows all three formats plus the implied probability, the profit on a $100 bet, and the total you get back if it wins.
American +150: 100 ÷ (150 + 100) = 100 ÷ 250 = 40.0%. Decimal: 1 + 150 ÷ 100 = 2.50. Fractional: 150 ÷ 100 = 3/2.
American −200: 200 ÷ (200 + 100) = 200 ÷ 300 = 66.7%. Decimal: 1 + 100 ÷ 200 = 1.50. Fractional: 100 ÷ 200 = 1/2.
Decimal 2.50: 1 ÷ 2.50 = 40.0%. Probability 40% back to odds: decimal = 1 ÷ 0.40 = 2.50, American = (2.50 − 1) × 100 = +150, fractional = (1 − 0.40) ÷ 0.40 = 0.60 ÷ 0.40 = 3/2.
Common conversions
Odds and implied probability, side by side
Every row below is the same price written three ways, with its implied probability:
| American | Decimal | Fractional | Implied probability |
|---|---|---|---|
| +300 | 4.00 | 3/1 | 25.0% |
| +200 | 3.00 | 2/1 | 33.3% |
| +150 | 2.50 | 3/2 | 40.0% |
| +100 | 2.00 | 1/1 | 50.0% |
| −110 | 1.91 | 10/11 | 52.4% |
| −150 | 1.67 | 2/3 | 60.0% |
| −200 | 1.50 | 1/2 | 66.7% |
| −300 | 1.33 | 1/3 | 75.0% |
The standard −110 line on a two-way bet implies 52.4% on each side — the two sides add to 104.8%, and the extra 4.8 points is the bookmaker margin.
Read the price before you bet
Plus odds are the underdog and minus odds are the favorite — +150 pays more because it is expected to win less often.
Compare the implied probability with your own judgment: a bet only has value if you think the real chance is higher than the implied chance.
Decimal odds include your stake, so 2.50 on $100 returns $250 in total — $150 profit plus your $100 back.
Shop around: the same outcome can be +150 at one book and +160 at another, and that 2.4-point gap in implied probability is free value.
Implied probability is not a prediction. It is the break-even chance the price assumes — the bookmaker margin means the real chance is a little lower.
Good to know
Frequently asked questions
What does +150 odds mean?
Plus odds show how much profit a $100 bet wins. At +150, a $100 bet wins $150 profit and returns $250 in total, and the implied probability is 40.0% — 100 divided by (150 + 100).
What does -200 odds mean?
Minus odds show how much you must risk to win $100. At -200, you risk $200 to win $100 profit, and the implied probability is 66.7% — 200 divided by (200 + 100). The minus sign marks the favorite; the plus sign marks the underdog.
How do you convert decimal odds to a percentage?
Divide 1 by the decimal odds and multiply by 100. Decimal odds of 2.50 give 1 divided by 2.50, which is 0.40, or 40.0%. Decimal odds of 1.50 give 1 divided by 1.50, which is 66.7%.
Why do the implied probabilities of both sides add up to more than 100%?
Because bookmakers build a margin, called the vig or overround, into the odds. If both sides of a two-way market imply 52.4% each, they add to 104.8%, and the extra 4.8 points is the bookmaker margin. This calculator converts one set of odds at a time and does not remove that margin.