Implied Probability Calculator - American, Decimal & Fractional Conversions

Input Type

American Odds

Enter positive odds (+150) for underdogs or negative odds (-150) for favorites

Remove Vig (Calculate Fair Odds)

Opposing Side Odds (for Vig Removal)

Enter the odds for the opposite outcome to calculate fair odds without vig

Options

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Decimal Places

Show Formula

Probability (%)

Enter probability as a percentage (e.g., 52.38 for 52.38%)

Sportsbook 1

Sportsbook 2

Sportsbook 3

Sportsbook 4

Your Estimated Probability (%)

Based on your analysis, what's the TRUE probability of this outcome?

Market American Odds

What odds is the sportsbook offering?

Wager Amount ($)

Enter your bet size for EV calculation

Common Betting Odds Conversions

American Odds	Implied Probability	Decimal Odds	Fractional Odds	Meaning
-500	83.33%	1.20	1/5	Heavy favorite
-400	80.00%	1.25	1/4	Heavy favorite
-300	75.00%	1.33	1/3	Strong favorite
-200	66.67%	1.50	1/2	Solid favorite
-150	60.00%	1.67	2/3	Moderate favorite
-110	52.38%	1.91	10/11	Slight favorite
+100	50.00%	2.00	1/1	Even money
+110	47.62%	2.10	11/10	Slight underdog
+150	40.00%	2.50	3/2	Moderate underdog
+200	33.33%	3.00	2/1	Solid underdog
+300	25.00%	4.00	3/1	Strong underdog
+400	20.00%	5.00	4/1	Heavy underdog
+500	16.67%	6.00	5/1	Heavy underdog

How Implied Probability Works

Why the conversion matters

Sportsbooks express price through odds, but betting decisions are easier to compare as probabilities. A -150 favorite converts to 60% implied probability. A +200 underdog converts to 33.33%. Those percentages show the break-even rate required before the bet can become profitable.

Implied probability is especially useful when comparing different bet types. If a football team is priced as a favorite on the spread, the Spread to Moneyline Converter can estimate the outright win probability implied by that point spread. Comparing that number with the posted moneyline can reveal which market is priced more efficiently.

Key concepts

Overround (Vig): Sportsbooks set odds so the implied probabilities of all outcomes total more than 100%. The amount above 100% represents the book's margin.
Fair Odds: The estimated price after removing vig. When both sides are -110, each side has a 52.38% implied probability, but the no-vig fair probability is 50% each.
Finding Value: Value exists when an independent probability estimate is higher than the market's implied probability. The difference is the edge.
Break-Even Point: The win rate required to avoid losing money at a given price. At -110, the break-even rate is 52.38%.

Conversion Formulas

American Odds to Implied Probability

Negative Odds (Favorites):

Probability = |Odds| / (|Odds| + 100)

Example: -150 → 150 / (150 + 100) = 60%

Positive Odds (Underdogs):

Probability = 100 / (Odds + 100)

Example: +200 → 100 / (200 + 100) = 33.33%

American Odds to Fractional Odds

Negative Odds: Fractional = 100 / |Odds|

Example: -150 → 100/150 = 2/3

Positive Odds: Fractional = Odds / 100

Example: +200 → 200/100 = 2/1

American Odds to Decimal Odds

Negative Odds: Decimal = (100 / |Odds|) + 1

Example: -150 → (100 / 150) + 1 = 1.67

Positive Odds: Decimal = (Odds / 100) + 1

Example: +200 → (200 / 100) + 1 = 3.00

Probability to American Odds

If Probability > 50%: Odds = -(Probability / (1 - Probability)) × 100

Example: 60% → -(0.60 / 0.40) × 100 = -150

If Probability < 50%: Odds = ((1 - Probability) / Probability) × 100

Example: 33.33% → ((0.6667) / 0.3333) × 100 = +200

Calculating Expected Value

Expected value compares an estimated win probability with the price offered by the market. The calculator does not decide whether the estimate is accurate, but it shows whether that estimate would be profitable at the listed odds.

Expected Value Formula:

EV = (Probability of Winning x Potential Profit) - (Probability of Losing x Stake)

Hypothetical Example Calculation

Example Calculation:

Estimated probability	55%
Market odds	+150 (40% implied)
Stake	$100

EV = (0.55 x $150) - (0.45 x $100)

EV = $82.50 - $45.00

EV = +$37.50

Positive EV detected. Edge: 15 percentage points (55% estimated vs 40% implied).

EV Percentage:

EV% = ((True Probability x Decimal Odds) - 1) x 100

EV% = ((0.55 x 2.50) - 1) x 100 = +37.5%

Decision Matrix:

EV > 0	Positive expected value
EV = 0	Break even scenario
EV < 0	Negative expected value

Sportsbook Profit Margins and No-Vig Odds

Most betting markets include sportsbook margin. The raw implied probability from one side of a market is useful, but it is not always the same as the fair probability. Removing vig creates a cleaner benchmark for comparing prices across sportsbooks.

Example: NFL Game

Team A: -110 (52.38% implied)
Team B: -110 (52.38% implied)
Total: 104.76% (4.76% is the vig)

Fair Odds (No Vig):

Each team: 50.00% probability
Each team: +100 American odds
Each team: 2.00 decimal odds

The 4.76% difference is the sportsbook's profit margin on every $100 wagered.

How to Remove Vig:

Convert both sides to implied probability
Add them together (e.g., 104.76%)
Divide each side by the total
Team A fair probability: 52.38% / 104.76% = 50%
Team B fair probability: 52.38% / 104.76% = 50%

For two-sided markets, the Vig Calculator is the faster way to remove the margin and compare fair odds side by side.

Implied Probability Calculator Questions

What is implied probability?

Implied probability is the conversion of betting odds into a percentage. It represents the likelihood of an outcome as reflected by the sportsbook's odds. For example, -150 odds converts to 60% implied probability, meaning the book prices this outcome as having a 60% chance of occurring.

How is implied probability calculated from American odds?

For negative odds (favorites), divide the absolute value of the odds by (absolute value + 100), then multiply by 100. For positive odds (underdogs), divide 100 by (odds + 100), then multiply by 100.

Example: -150 becomes 150/(150+100) = 60%
Example: +200 becomes 100/(200+100) = 33.33%

Why is implied probability higher than true probability?

Sportsbooks build a profit margin (vig or juice) into their odds. When you add the implied probabilities of all possible outcomes, the total exceeds 100%. This excess is the book's edge. For example, if both sides of a bet are -110 (52.38% each), the total is 104.76%, with the extra 4.76% representing the sportsbook's profit margin.

What are fair odds after removing vig?

Fair odds represent the true probability after removing the sportsbook's profit margin. Calculate by converting both sides to implied probability, adding them together, then dividing each side by the total. If both sides are -110 (52.38%), the total is 104.76%. Divide each: 52.38/104.76 = 50% fair probability for each side, which converts to +100 (even money) American odds.

Is implied probability the same as true probability?

No. Implied probability is the break-even percentage created by the posted odds. True probability is an independent estimate of how often the outcome should happen.

How are different sportsbooks compared with implied probability?

Convert each sportsbook's odds to implied probability for the same outcome. The lowest implied probability usually represents the better price because the bet requires a lower win rate to break even.