🎲 Expected Value Calculator
Your probability estimate vs the market's price — what's the trade actually worth after fees?
What expected value tells you
Expected value (EV) is the average profit or loss a trade would produce if you could repeat it forever. A positive-EV trade makes money over the long run even when individual outcomes go against you; a negative-EV trade bleeds money no matter how many times it happens to win. On Kalshi, EV comes down to one comparison: the probability you believe versus the price the market charges. This calculator turns that comparison into a dollar figure — after fees.
Enter your probability
Give your honest estimate of how likely the outcome is, as a percentage. This is your edge's foundation — be realistic, not hopeful.
Add the price and size
Enter the Kalshi price in cents and how many contracts you'd buy. The price is what you pay; if you're right, each contract settles at 100¢.
See gross and net EV
The calculator shows expected value before fees, the taker fee on entry, and your net EV and expected ROI after costs.
Act on the verdict
Positive net EV means the price is in your favor given your estimate. Negative means you're the one overpaying — pass, or wait for a better entry.
Frequently asked questions
How is expected value calculated on Kalshi?
Per contract, EV = p × (100 − price) − (1 − p) × price, in cents, where p is your probability and price is the cost in cents. Multiply by your contract count and subtract the taker fee to get net EV. The calculator does this automatically.
What does +EV actually mean?
It means that at this price, your probability estimate implies you'd profit on average over many identical trades. It does not guarantee this specific trade wins — variance is real. +EV is about being a long-run favorite, not a lock.
Why does my probability estimate matter so much?
EV is entirely driven by the gap between your probability and the market's. If your estimate is wrong, a trade the calculator labels +EV can be deeply −EV in reality. Garbage in, garbage out — your edge is only as good as your read.
How does EV relate to Kelly sizing?
EV tells you whether a trade is worth making; Kelly tells you how much to stake on it. Use this calculator to confirm an edge exists, then the Kelly Sizer to size the position without overbetting.