Expected Value (EV) Calculator
Find mathematically profitable bets on Polymarket and Kalshi by comparing your estimated probability against the market price.
1. Bet Details
Current price on Polymarket (e.g., 40¢)
What you think the REAL chance of winning is
2. Analysis
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What is Expected Value (EV)?
Expected Value (EV) measures the average amount you would win or lose per bet if you placed the same bet thousands of times. It is the single most important concept in professional betting.
✅ Positive EV (+EV)
Means the bet is profitable in the long run. If you find a Polymarket event priced at 40¢ (40%) but you believe the true probability is 50%, this is a +EV bet.
❌ Negative EV (-EV)
Means you will lose money over time. Most bets are -EV due to market efficiency and fees. Avoid these bets even if you think they "might" win this one time.
How it is Calculated
EV = (Potential Profit * True Probability) - (Potential Loss * True Probability of Losing)
In Prediction Markets (binary $1 payout):
EV = ($1 * True %) - Cost