Learn how to convert betting odds into implied probability, calculate overrounds, and identify when bookmakers have mispriced a market.

In This Guide

What Is Implied Probability?

Implied probability is the likelihood of an outcome as suggested by the betting odds.

It tells you what the bookmaker thinks the chances are — and how you can compare that to your own assessment.

Every set of odds has an implied probability hidden inside it.

Decimal odds: Probability = 1 / odds. So 2.50 odds = 1/2.50 = 40%.

Fractional odds: Probability = denominator / (numerator + denominator). So 3/1 = 1/4 = 25%.

American odds: Positive: Probability = 100 / (odds + 100). Negative: Probability = odds / (odds + 100).

Decimal	Fractional	American	Implied Prob
1.33	1/3	-300	75.0%
1.50	1/2	-200	66.7%
2.00	Evens	+100	50.0%
3.00	2/1	+200	33.3%
6.00	5/1	+500	16.7%
11.00	10/1	+1000	9.1%

In a fair market, implied probabilities add up to exactly 100%. In reality, they always add up to more.

If a football match has odds of 2.10/3.40/3.60, the implied probabilities are 47.6% + 29.4% + 27.8% = 104.8%.

That extra 4.8% is the bookmaker's margin — their built-in profit. Lower is better for bettors.

To estimate true probability, remove the overround from each selection proportionally.

Compare multiple bookmaker lines — the sharpest prices (lowest margin) are closest to true probability.

Pinnacle is widely regarded as the sharpest bookmaker, so their odds are often used as a proxy for true probability.

Tip: Use wagerbase Steam Moves to see when sharp money moves a line — this often reveals the true probability.

When your estimated probability exceeds the implied probability, you have found value.

Track your predictions against actual outcomes over hundreds of bets to calibrate your probability assessments.

Even small edges compound significantly over time with disciplined staking.

Track line movements and sharp money. Steam Moves →

For more guides, tools, and analysis, visit wagerbase.