Odds Converter
Convert between fractional, decimal, American, implied probability, and Hong Kong odds formats.
Odds Converter
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Formula: Implied Probability = (1 / Decimal Odds) x 100
Worked example — Decimal: 3.25 | American: +225 | Fractional: 9/4 | Implied: 30.77% | Profit: $112.50
Formula
Implied Probability = (1 / Decimal Odds) x 100
All odds formats can be converted through decimal odds as an intermediary. Decimal odds represent total return per unit staked. Dividing 1 by decimal odds gives the implied probability, which is the foundation for all conversions.
Worked Examples
Example 1: Converting Decimal Odds to All Formats
Problem:A bookmaker offers decimal odds of 3.25 on a football match. Convert to all formats and calculate payout on a $50 bet.
Solution:Decimal: 3.25 American: (3.25 - 1) x 100 = +225 Fractional: 2.25/1 = 9/4 Implied Probability: (1/3.25) x 100 = 30.77% Hong Kong: 3.25 - 1 = 2.25 Payout: $50 x 3.25 = $162.50 Profit: $162.50 - $50 = $112.50
Result:Decimal: 3.25 | American: +225 | Fractional: 9/4 | Implied: 30.77% | Profit: $112.50
Example 2: Converting American Odds (Favorite)
Problem:A tennis player is listed at -180 American odds. Convert and calculate payout on a $200 bet.
Solution:American: -180 Decimal: (100/180) + 1 = 1.5556 Fractional: 0.5556/1 = 5/9 Implied Probability: (1/1.5556) x 100 = 64.29% Hong Kong: 0.5556 Payout: $200 x 1.5556 = $311.11 Profit: $311.11 - $200 = $111.11
Result:Decimal: 1.5556 | Fractional: 5/9 | Implied: 64.29% | Profit: $111.11
Frequently Asked Questions
What are the main odds formats used in sports betting worldwide?
The three primary odds formats are decimal (European), fractional (British), and American (moneyline). Decimal odds represent the total payout per unit staked, including your stake, so 2.50 means you receive $2.50 for every $1 wagered. Fractional odds show profit relative to stake, so 3/2 means $3 profit for every $2 staked. American odds use a baseline of $100: positive odds like +150 show profit on a $100 bet, while negative odds like -200 show how much you must bet to win $100. Beyond these, Hong Kong odds show profit per unit (similar to fractional but as a decimal), Indonesian odds work like American but based on 1 unit instead of 100, and Malay odds have their own inverted format popular in Southeast Asian markets.
How do you convert between decimal and American odds?
Converting between decimal and American odds follows two rules depending on whether the decimal odds are above or below 2.0 (even money). For decimal odds of 2.0 or higher (underdog), subtract 1 then multiply by 100 to get positive American odds. For example, decimal 3.50 becomes (3.50 - 1) x 100 = +250. For decimal odds below 2.0 (favorite), divide -100 by the decimal minus 1. For example, decimal 1.50 becomes -100 / (1.50 - 1) = -200. Going the other direction: positive American odds are divided by 100 then add 1 for decimal. So +250 becomes (250/100) + 1 = 3.50. Negative American odds use 100 divided by the absolute value then add 1. So -200 becomes (100/200) + 1 = 1.50.
What is implied probability and how does it relate to odds?
Implied probability converts odds into a percentage representing the likelihood of an outcome as suggested by the odds. It is calculated as 1 divided by the decimal odds, then multiplied by 100. Decimal odds of 2.00 imply a 50% probability. Odds of 4.00 imply 25%. Odds of 1.25 imply 80%. Understanding implied probability is crucial because it allows bettors to compare bookmaker odds against their own estimated probability of an outcome. If you believe a team has a 60% chance of winning but the odds imply only 45%, the bet offers positive expected value. However, bookmaker margins mean the sum of implied probabilities for all outcomes exceeds 100%, creating the overround or vigorish that represents the bookmaker profit margin.
What is the overround and how does it affect betting odds?
The overround, also called vigorish or juice, is the built-in profit margin that bookmakers embed in their odds. In a fair market, the implied probabilities of all possible outcomes sum to exactly 100%. Bookmakers set odds so this sum exceeds 100%, with the excess being their margin. For example, in a two-outcome event, a fair coin flip would be 2.00 on each side (50% + 50% = 100%). A bookmaker might offer 1.91 on each side, implying 52.4% each, totaling 104.7%. The 4.7% overround is the bookmaker margin. Lower overrounds indicate more competitive odds and better value for bettors. Sharp bettors always compare overrounds across bookmakers to find the best value and minimize the house edge on their wagers.
How do Hong Kong, Indonesian, and Malay odds formats work?
These three Asian odds formats each represent payouts differently and are widely used in their respective regional markets. Hong Kong odds show the net profit per unit staked, essentially the decimal odds minus 1. So Hong Kong odds of 1.50 equal decimal 2.50, meaning $1.50 profit per $1 bet. Indonesian odds work similarly to American odds but use 1 unit instead of 100 as the base. Positive Indonesian odds of 1.50 mean $1.50 profit per $1 bet (same as Hong Kong). Negative Indonesian odds of -1.50 mean you risk $1.50 to win $1. Malay odds are inverted from Indonesian: positive Malay odds below 1.0 represent underdogs showing your profit per unit, while negative Malay odds show what you risk to win one unit. These formats are standard across Asian sportsbooks and betting exchanges in the region.
How do you convert fractional odds into decimal odds?
Divide the numerator by the denominator and add one, because decimal odds include the returned stake while fractional odds show only the profit. Odds of 5/2 become 5 divided by 2 plus 1, which is 3.50, so a 10 unit stake returns 35 including the stake. Going the other way, subtract one from the decimal figure and express the remainder as a fraction: 3.50 minus 1 is 2.5, which is 5/2. Fractions with awkward denominators such as 11/8 are the main reason decimal odds have largely replaced them in modern markets.
What are even money odds in every format?
Even money means the profit equals the stake. It is 1/1 in fractional form, 2.00 in decimal and plus 100 in American odds, and it carries an implied probability of 50 percent since 1 divided by 2.00 is 0.5. It sits exactly at the boundary of the American system, where prices above it use positive numbers showing profit on a 100 unit stake and prices below it use negative numbers showing the stake needed to win 100. Recognising this anchor makes it easy to sanity check any conversion.
Why do American odds have no values between minus 100 and plus 100?
The two branches of the American system meet at even money and then diverge. Plus 100 and minus 100 both describe a doubled return, so they are the same price written two ways, and there is nothing between them left to describe. Prices on the favourite side move away from minus 100 toward larger negative numbers, and prices on the underdog side move away from plus 100 toward larger positive numbers. This discontinuity is why American odds cannot be averaged or interpolated directly; convert to decimal or implied probability first.
How do you strip the bookmaker margin out to find fair odds?
Convert every selection in the market to implied probability, then add them. The total will exceed 100 percent by the overround. The simplest correction divides each implied probability by that total so the adjusted set sums to exactly one, which is the multiplicative or proportional method. Inverting each adjusted probability gives fair decimal odds. This assumes the margin is spread evenly across selections; on markets with a heavy longshot bias the margin is loaded onto the outsiders, so proportional stripping will slightly flatter them.
What is the difference between the vig and the overround?
They describe the same margin from two angles. The overround is how far the summed implied probabilities exceed 100 percent, so a two-way market totalling 104.8 percent has a 4.8 percent overround. The vig, or hold, is the share of total staked money the book expects to keep, which for that market is 4.8 divided by 104.8, or about 4.6 percent. Overround is the easier figure to compute from a price list, while hold is the correct figure for comparing profitability across markets with different numbers of selections.
References
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
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