Implied Probability Calculator

Understanding Probability

1

What is implied probability and how is it calculated?

Implied probability is the percentage chance of winning that the odds suggest, including the bookmaker's margin (vig). For American odds: Positive = 100 ÷ (odds + 100), Negative = |odds| ÷ (|odds| + 100). For decimal odds: 1 ÷ decimal odds. For fractional odds: denominator ÷ (numerator + denominator). Example: +150 odds = 100 ÷ 250 = 40% implied probability.

2

How do I convert American odds to implied probability?

For positive American odds: Implied Probability = 100 ÷ (odds + 100) × 100. For negative American odds: Implied Probability = |odds| ÷ (|odds| + 100) × 100. Examples: +200 = 100 ÷ 300 = 33.33%. -150 = 150 ÷ 250 = 60%. Our calculator handles all conversions automatically.

3

What is the difference between implied and fair probability?

Implied probability includes the bookmaker's margin (vig), while fair probability represents the true market assessment without vig. Fair probability is found using no-vig odds. For example, if both teams are -110, implied probability is 52.4% each (104.8% total), but fair probability is 50% each (100% total). The 4.8% difference is the vig.

4

How do I use implied probability for value betting?

Compare the implied probability to your assessment of true probability. If your probability is higher than the implied probability, you have a value bet. Example: You think a team has 55% chance to win, but odds imply 50%. This is a +5% edge. Only bet when your probability greater than implied probability to ensure positive expected value.

5

Why do implied probabilities add up to more than 100%?

Implied probabilities exceed 100% because they include the bookmaker's margin (vig). For example, -110 odds on both sides = 52.4% + 52.4% = 104.8%. The extra 4.8% is the bookmaker's profit margin. Use our No-Vig Calculator to remove the vig and find fair probabilities that add up to exactly 100%.

6

What is a good implied probability for betting?

There's no "good" implied probability - it depends on your assessment of true probability. Focus on finding value where your probability greater than implied probability. A 40% implied probability bet can be excellent if you think the true probability is 45%. A 60% implied probability bet can be terrible if you think the true probability is 55%. Always compare to your own analysis.