Tools
Expected value calculator
Is a contract worth buying at this price? Enter the price, your probability, the number of contracts and the fee. The calculator shows your expected profit, the return on what you pay, and the probability at which the trade breaks even.
Expected value calculator
- Expected profit
- $9.00 ($0.09 per contract)
- Expected return
- 14.8%
- Break-even probability
- 61.0%
The formula
EV per contract = p(win) × $1 − (price + fee)
What expected value tells you
Expected value is what a trade earns on average if you could repeat it many times at your probability. A contract that costs c and pays $1 has an expected value of q − c, where q is your probability of winning. Positive means the price is below your estimate; negative means you are paying more than you think it is worth.
Worked example: YES at 60¢, you think 70%, 1¢ fee. Each contract is expected to earn 0.70 − 0.61 = 9¢, a 14.8% expected return, and the trade breaks even at 61%.
What it does not tell you
A positive expected value is not a likely profit on one trade: a 70% event still loses three times in ten. It also assumes you can buy at the price you entered — on a thin order book a large order moves the price against you, which our guide to liquidity and spreads explains.
Frequently asked questions
- How do I calculate expected value on a prediction market?
- Multiply your probability of winning by the $1 payout and subtract what you pay per contract, fees included: EV = q − (price + fee).
- What is the break-even probability?
- The probability at which expected value is zero — the price plus fee. If you believe the event is more likely than that, the trade has positive expected value.
Not financial advice. These calculators do arithmetic on the numbers you enter; they do not know a platform’s current prices or whether it is open to you. Check both in the platform reviews.