Expected Value (EV) Calculator
Quantify whether a bet is profitable long-term by comparing the price to its true probability.
Betting Details
The book's price versus your true probability.
+150 · 2.50 · 3/2 · 40.0%
From a sharp book's no-vig line, your model, or a prediction-market contract price (¢ = %).
✅ Positive EV (+EV)
Profitable over the long run.
Long-term expectation:
+$12.50
EV % (ROI)+12.50%
Book implied prob.40.00%
Your edge5.00 pts
How to use this tool
- Enter your stake and the sportsbook price (any format).
- Enter the true win probability from a sharper source.
- A positive result means the book is mispricing the outcome in your favour.
The formula
EV = (decimal × stake × p) − stake- decimal = book price as decimal odds
- p = true win probability (0–1)
- Edge = p − book implied probability
Worked example
$100 at +150 (2.50) with a true probability of 45%: EV = 2.50 × 100 × 0.45 − 100 = +$12.50 (a +12.5% ROI bet) because 45% > the book's 40% implied.
Prediction markets as a probability source: a near-vig-free Kalshi/Polymarket price is one of the cleanest "true probability" inputs available — a contract at 58¢ ⇒ enter 58.