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Prediction Market Expected Value Calculator

Determine if a bet has positive expected value.

Odds Type
$
%

Results

Expected Value

$5.00

EV %

5.00%

+EV

What does this calculator do?

The Expected Value (EV) calculator estimates the average profit or loss you would expect over many identical bets given a quoted price and your own win probability. EV is the foundational concept that ties together pricing, edge, and bankroll management. Positive EV doesn't guarantee a single bet will win, but it does indicate that — if your probabilities are well-calibrated — the same decision repeated over time should come out ahead.

Start by entering a stake, a set of odds, and your best estimate of the chance of winning. You can use American moneyline odds (e.g., −110 or +150) or prediction-market style prices (e.g., 0.60 means sixty cents for a $1 payoff). We convert the odds into payoff and cost per unit, then compute EV as: prob × profit_if_win − (1 − prob) × stake. For moneyline odds, the stake is the cash you wager. For prediction-market prices, a “unit” pays $1 on success and costs p dollars up front, so we scale your stake into contract units behind the scenes.

What does the result mean in practice? If the EV shows +$3.50, that's the average profit you'd expect per bet if you could place that same wager thousands of times under the same conditions. EV is especially useful when comparing multiple options or deciding whether to chase a line move. Even a small positive EV can be worth taking if your bankroll strategy supports it and the variance is manageable; a small negative EV will grind your bankroll down over time.

Keep in mind that fees and slippage can change the picture. This basic EV assumes clean fills and no platform fees. If you're betting on prediction markets, consider pairing this tool with the Market Fees calculator to adjust your effective price. If you're comparing book lines, our Vig calculator can help you understand how much margin you're paying. Use all three together — EV, Market Fees, and No-Vig Fair Odds — to form a realistic view of whether a bet is worth it.

Frequently Asked Questions

How do you compute EV for each odds type?

For American moneyline odds, we convert to decimal payoff: +150 means you win $1.50 per $1 wagered, so EV = (prob × 1.50) − (1 − prob) × 1. For negative odds like −110, the payoff is 100/110 ≈ 0.909 per $1. For prediction market prices, a contract priced at 0.60 costs $0.60 and pays $1 if it wins — we scale your dollar stake into contract units so the output is still in dollars.

Does this include fees?

No. This calculator assumes clean fills with no platform fees. To get fee-adjusted EV for prediction markets, use the Market Fees calculator first to find your true effective price, then re-enter that adjusted price here.

What’s a good EV threshold to act on?

There’s no universal threshold — it depends on your bankroll, variance tolerance, and edge confidence. As a rule of thumb, most disciplined traders require at least +2-3% EV before entering a position, to leave room for slippage, fees, and probability estimation error.