A bet is +EV if, at the price you took, your estimated probability is higher than the market’s implied probability.
If that condition is not met, it is not a +EV decision, even if it wins.
Step 1: Calculate Implied Probability
Implied Probability (%) = 1 ÷ Odds × 100
Example:
Odds 2.10 → 1 ÷ 2.10 = 47.62%
This is the market’s break-even expectation.
Step 2: Define Your Estimated Probability
You must have an independent estimate:
“I believe this outcome occurs X% of the time.”
If you cannot state a percentage, you cannot judge EV properly.
Step 3: Compare the Two
If:
Your Probability > Implied Probability → +EV
Your Probability = Implied Probability → Break-even (0 EV)
Your Probability < Implied Probability → -EV
Example:
Implied probability: 47.62%
Your estimate: 52%
This is +EV if your estimate is accurate.
Step 4: Check the Price You Actually Got
Value depends on the exact odds you took, not the general idea of the bet.
If the line moved and you took a worse price, EV can disappear.
Selection alone is not enough. Price determines EV.
Step 5: Confirm Stake Discipline
Even a +EV bet can be executed poorly if staking is wrong.
A +EV decision must also:
Fit your bankroll rules
Be sized in units
Avoid emotional sizing
Good EV with reckless stakes increases risk of ruin.
Practical Self-Test
To confirm +EV, you should be able to state:
The odds taken
The implied probability
Your estimated probability
The reason for your probability advantage
That your stake followed your rules
If any part is missing, you cannot confidently claim +EV.
Core Principles
+EV means your probability estimate exceeds implied probability at the price you took.
Outcome does not define EV.
Price matters more than selection.
A percentage estimate is required.
Execution must match bankroll rules.
