Expected Value Calculator

What the number means

Expected value is the average result per bet if you could make the identical bet an unlimited number of times at the same price with the same true probability. It is not a forecast of any single bet, all of which resolve to either a win or a loss and never to the average.

The compact form is worth memorising: EV% = p x D - 1. If your probability multiplied by the decimal price is above 1, the bet is positive expectation; if it is below 1, it is not. Everything else on this page is that one line rearranged.

Where it misleads

The output is only as good as the probability you typed, and that is the input nobody can check. A calculator that says a bet is +6% EV is really saying "if your 55% is correct, this is +6%". Estimating win probability to within a point or two, repeatedly, against a market that prices thousands of events, is the entire difficulty of the activity. The arithmetic is the easy half.

The N-bet projection assumes independent bets at a fixed price and a fixed edge. Real sequences are correlated, prices move against you as you bet into them, limits arrive, and the edge you had at open is often gone by close. Read the projection as an illustration of how slowly a small edge compounds, not as a target. Even a genuine 3% edge spends long stretches underwater, and distinguishing that from having no edge takes a sample far larger than most bettors ever accumulate.