Expected Value Calculator
Enter the market price and your estimated probability to see whether a trade is +EV and how large your edge is.
$0.50
$0.01$0.50$0.99
60%
1%50%99%
Edge: +10.0 percentage points
$
Buy Yes200.0 shares @ $0.50 + $2.00 fee
Total EV
+$18.00
EV per Share
+$0.09
Edge
+10.0%
EV = (true probability × shares) − stake − fee. Fee formula: fee = shares × 0.04 × p × (1 - p). Maker orders pay zero fees.
How Expected Value Works
Expected value is the average profit or loss you’d expect per trade if you repeated it under the same conditions. A positive EV trade profits over time; a negative EV trade loses.
EV depends on three things: the cost of entering (market price plus fees), the payout ($1.00 per share if correct), and the true probability of the outcome. The market price is the crowd’s estimate; if yours is more accurate, the gap is your edge.
Frequently Asked Questions
What is expected value in prediction markets?
Expected value (EV) is the average profit or loss per trade if you repeated it many times. A +EV trade profits over time; a -EV trade loses. EV = (true probability × payout) − cost − fees.
What is edge?
Edge is the gap between your estimated probability and the market's implied probability. If the market prices an outcome at 50% and you believe 65%, your edge is +15 points — the larger the edge, the higher your expected value.
How confident should I be before trading?
Only trade when your edge comfortably exceeds the fee. A thin edge (a few points) can flip to negative if your estimate is even slightly wrong.