Value Bet Calculator
Enter the bookmaker's decimal odds and your estimated probability. The calculator instantly shows your expected value (EV) and optimal stake size using the Kelly Criterion.
Calculate Expected Value
The odds displayed on Bet9ja for your selection.
Your honest assessment of the outcome's true chance.
Bookmaker's Implied Prob.
40.0%
EV per ₦100
+₦25.0
Verdict
Quarter Kelly Stake
4.2%
(Full: 16.7%)
How Expected Value Works
Expected Value (EV) tells you how much you'll win or lose per ₦100 staked over the long run. Here's the formula:
A positive EV means the bet is profitable long-term. But here's the thing: you need to be honest about your probability estimate. Overestimating your edge turns a losing bet into a false "value bet."
For a deeper breakdown with worked examples, read our complete value betting guide.
Kelly Criterion: How Much to Stake
Finding a value bet is step one. Step two is sizing your stake correctly. The Kelly Criterion formula calculates the mathematically optimal stake:
where b = odds − 1, p = your probability, q = 1 − p
Full Kelly is aggressive. Most serious punters use Quarter Kelly (25% of the suggested stake) to smooth out variance. This is what we display above.
Combine this with proper bankroll management to protect your funds during inevitable losing streaks.
Example Scenarios
| Scenario | Odds | Your Prob. | EV/₦100 | Verdict |
|---|---|---|---|---|
| Home favourite | 1.80 | 60% | +₦8.0 | Value |
| Draw at fair price | 3.00 | 33% | ₦-1.0 | No Value |
| Underdog with edge | 4.50 | 28% | +₦26.0 | Value |
| Over-priced favourite | 1.40 | 70% | ₦-2.0 | No Value |
| BTTS with stats edge | 2.10 | 55% | +₦15.5 | Value |
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