Implied Probability Calculator

How to Calculate Implied Probability from Odds

Implied probability tells you how likely a bookmaker thinks an outcome is, based on the odds they offer. It's the single most important number in value betting — because if you can consistently find outcomes where the true probability is higher than the implied probability, you'll profit long-term.

Decimal Odds → Implied Probability

Formula: Implied Probability = (1 ÷ Decimal Odds) × 100

Example: Odds of 2.50 → (1 ÷ 2.50) × 100 = 40%

American Odds → Implied Probability

Positive (+): Implied Probability = (100 ÷ (Odds + 100)) × 100

Example: +200 → (100 ÷ 300) × 100 = 33.33%

Negative (−): Implied Probability = (|Odds| ÷ (|Odds| + 100)) × 100

Example: −150 → (150 ÷ 250) × 100 = 60%

Fractional Odds → Implied Probability

Formula: Implied Probability = (Denominator ÷ (Numerator + Denominator)) × 100

Example: 3/1 → (1 ÷ (3 + 1)) × 100 = 25%

Why Implied Probability Matters

Bookmakers build a margin (overround) into their odds. That's why if you add up the implied probabilities of all outcomes in a market, the total usually exceeds 100%. The excess is the bookie's edge. Understanding implied probability lets you:

• Find value bets — where your estimated probability beats the implied probability
• Compare odds across bookmakers — the lowest implied probability = best value
• Calculate the bookmaker's margin — using our Overround Calculator
• Size your stakes correctly — with the Dutching Calculator

Frequently Asked Questions

What is implied probability?

Implied probability is the likelihood of an outcome as suggested by the bookmaker's odds. It converts odds into a percentage representing the chance of that outcome occurring. For example, decimal odds of 2.00 imply a 50% probability.

How do you calculate implied probability from decimal odds?

Divide 1 by the decimal odds, then multiply by 100. Formula: Implied Probability = (1 / Decimal Odds) × 100. For odds of 1.80: (1 / 1.80) × 100 = 55.56%.

How do you convert American odds to implied probability?

For positive American odds: (100 / (Odds + 100)) × 100. For negative American odds: (|Odds| / (|Odds| + 100)) × 100. For example, +150 gives (100/250)×100 = 40%, and -150 gives (150/250)×100 = 60%.

Why is implied probability important in betting?

Implied probability helps you identify value bets. If your estimated true probability is higher than the implied probability from the odds, you've found a value bet. It also reveals the bookmaker's margin when all outcomes' implied probabilities exceed 100%.

What does it mean when implied probabilities add up to more than 100%?

When the sum of implied probabilities for all outcomes exceeds 100%, the difference is the bookmaker's margin (overround or vig). For example, if a two-way market sums to 104%, the bookmaker's margin is 4%.