Betting Odds Calculator
Not all bets are created equal. This calculator helps you determine whether a bet offers positive expected value (+EV) based on the odds offered and your estimate of the true probability. Enter the decimal odds from your bookmaker and your honest assessment of the win probability. The calculator reveals the implied probability built into the odds and shows your expected profit or loss per bet over time. Use this to make more informed betting decisions based on mathematical edge rather than gut feeling.
How We Calculate This
Expected Value (EV) = Stake × (Probability × Odds - 1). Implied Probability = 1 / Odds. ROI = (Probability × Odds - 1) × 100%. A bet is +EV when your estimated probability exceeds the implied probability (i.e., Probability > 1/Odds).
Frequently Asked Questions
What is Expected Value (EV) in betting?
Expected Value is the average amount you'd win or lose per bet if you made the same bet many times. A positive EV (+EV) means the bet is mathematically profitable long-term. EV = Stake × (Your Probability × Odds - 1). For example, a €10 bet at 2.50 odds with a 50% chance of winning has EV = 10 × (0.50 × 2.50 - 1) = €2.50.
What is implied probability?
Implied probability is what the bookmaker's odds suggest the true probability should be. It's calculated as 1 ÷ Decimal Odds. For example, odds of 2.00 imply a 50% probability (1/2.00 = 0.50). If you believe the actual probability is higher than the implied probability, you have an edge.
How do I convert between odds formats?
Decimal odds are used here. To convert: Fractional to Decimal: add 1 to the fraction (5/1 = 6.00). American to Decimal: for positive odds, divide by 100 and add 1 (+200 = 3.00); for negative odds, divide 100 by the absolute value and add 1 (-150 = 1.67).
Why is my probability estimate important?
Your probability estimate is the key input. The implied probability just tells you what the odds assume. If you consistently estimate probabilities more accurately than the bookmaker, you can find +EV bets. Be honest with your estimates - overconfidence leads to losses.
Does positive EV guarantee profit?
No. Positive EV means you're favored mathematically in the long run, but short-term variance is high. You can lose many +EV bets in a row. The edge only shows over many bets. Never bet more than you can afford to lose, and consider bankroll management strategies.
Related Calculators
You might also find these calculators helpful: Compound Interest Calculator, Lost Socks Probability Calculator, and Shark Attack Calculator.
This calculator is for educational purposes only. Gambling involves risk and can be addictive. Never bet more than you can afford to lose. Past results do not guarantee future outcomes. Please gamble responsibly.