🧮 Odds Calculator — NJD

Compare your model probability to a sportsbook line. See fair odds, implied probability, edge, expected value, and Kelly stake sizing.

Inputs

Enter your model probability and the sportsbook’s American odds to compare price versus value.

Example: enter 61.5 if your model says this team wins 61.5% of the time.
Enter the sportsbook line in American odds, like -110, -145, or +125.
This is the amount you are planning to risk on the bet.
Your total betting bankroll used for Kelly sizing.
Many bettors use half Kelly or quarter Kelly to reduce volatility.
 
Fair Decimal Odds
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Fair American Odds
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Sportsbook Implied Probability
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Edge
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Profit if Bet Wins
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Expected Profit
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Expected Value (%)
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Full Kelly Stake
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Selected Kelly Stake
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1. Model Win Probability

This is your model’s estimate of how often the team should win. For example, 60% means the model expects the team to win 60 times out of 100.

2. Fair Odds

Fair odds are the no-vig odds implied by your model. In other words, this is the “break-even” price your model thinks is fair.

Fair Decimal Odds = 1 / Probability
Fair American Odds = convert the fair probability into American odds

3. Sportsbook Implied Probability

The sportsbook’s odds can be converted into a probability. That tells you what win chance the book is pricing in.

For positive odds: 100 / (odds + 100)
For negative odds: abs(odds) / (abs(odds) + 100)

4. Edge

Edge compares your model probability to the sportsbook’s implied probability.

Edge = Model Probability − Sportsbook Implied Probability

A positive edge means your model thinks the sportsbook is offering a better price than it should.

5. Expected Profit and EV%

Expected profit estimates your average profit or loss per bet if you could place the same bet many times at the same odds.

Expected Profit = (Probability × Profit if Win) − ((1 − Probability) × Bet Amount)
EV% = Expected Profit / Bet Amount

6. Kelly Stake

Kelly sizing suggests how much of your bankroll to bet based on your edge and the payout. Full Kelly is aggressive. Many bettors use half Kelly or quarter Kelly.

Kelly % = ((b × p) − q) / b
where b = decimal odds minus 1, p = your win probability, and q = 1 − p.

Quick interpretation

Fair odds are the no-vig odds implied by your model probability.

Edge is your model probability minus the sportsbook’s implied probability.

Positive EV means your model says the sportsbook price is better than it should be.