What is expected value in prediction markets?

Expected value (EV) is your average profit per dollar staked if you made the same trade many times. If your estimated probability is higher than the market-implied probability, EV is positive — the trade is worth making. Negative EV trades should be skipped regardless of confidence.

How do I use the EV Calculator for Polymarket?

Enter the current Polymarket contract price (in cents, e.g. 62 for a 62¢ YES contract), your own probability estimate, and your stake. The calculator shows whether the trade has positive EV and by how much — your edge per dollar staked.

What is a good expected value for a Polymarket trade?

Any positive EV is theoretically worth taking, but experienced traders typically target at least +5% EV to account for transaction costs and execution risk. Large positive EV (>15%) often signals either a genuine mispricing or a market with very low liquidity where your price impact matters.

Expected Value Calculator — EV & Edge for Prediction Markets

Trade Parameters

Market Price (YES %) 55%

Your Win Probability 65%

Stake ($) $100

🎯 Scan markets for edge — Poly-Sim Score 📐 Kelly Criterion — how much to bet

+$18.18

Expected Value per trade

10.0%

Edge %

55.0%

Implied prob

18.2%

Expected ROI

$81.82

Max win

✅ Positive EV: You expect to earn +$18.18 per $100 staked with a 10.0% edge.

EV scenarios at different stake sizes

⚡ Quick Summary

What it does: Calculates whether a trade has positive or negative expected value — the fundamental gate between disciplined trading and gambling.
Formula: EV = (p × Win) − (1 − p) × Stake, where p is your probability estimate and Win is your profit if correct.
Key insight: Even a 5% edge compounds to massive returns over 100+ trades. A −2% edge compounds to ruin. EV sign matters more than individual outcomes.
Bottom line: Never enter a Polymarket position without confirming positive EV first. If your p estimate equals the market price, your EV is zero — skip it.

What Is Expected Value in Trading?

Expected Value (EV) is the cornerstone of professional trading, sports betting, and prediction market strategy. It answers: If I made this same trade thousands of times, would I profit or lose on average?

EV Formula for Prediction Markets

EV = (p × Win) − (1−p) × Stake Where: p = your probability estimate Win = (Stake / Price) − Stake (profit if YES resolves)

How to Find Edge on Polymarket

Information advantage — you read a primary source before the market reacts
Model advantage — you have a quantitative model that outperforms crowd intuition
Structural mispricing — low-liquidity markets have wider spreads
Recency bias exploitation — crowds over-update on recent news events

💼 Track your performance — CoinLedger 📖 Deep dive: EV in trading →

Expected Value Calculator

What Is Expected Value in Trading?

EV Formula for Prediction Markets

How to Find Edge on Polymarket

Related Tools & Guides

Found your edge? Apply it on Polymarket now →