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Expected Value (EV) Explained + Simple Calculator

Expected value (EV) is the math behind “good bets.” A bet can lose today and still be a profitable decision long-term — EV tells you which is which.

What is expected value?

Expected value (EV) is the average amount you would win or lose per bet if you could repeat the same wager many times under the same conditions.

Positive EV doesn’t guarantee a win today. It means your decision has an edge over the long run.

The EV formula (plain English)

EV = (Win Probability × Profit if Win) − (Loss Probability × Stake)

If the result is above 0, the wager is positive EV.

Worked example

You bet $100 at +150. If you win, profit is $150. If you lose, you lose $100.

  • Your estimated win probability: 45%
  • Loss probability: 55%

EV = (0.45 × 150) − (0.55 × 100) = 67.50 − 55 = +12.50

EV = +$12.50 per $100 bet (a good bet, mathematically).

Simple EV “calculator” (manual steps)

  1. Convert odds to payout profit (not total return).
  2. Estimate win probability as a decimal (e.g., 52% → 0.52).
  3. Compute EV using the formula above.

Tip: start by learning implied probability so you can compare the sportsbook’s number to your estimate.

EV vs. win rate (why beginners get confused)

High win rate doesn’t automatically mean profit (e.g., laying -300 repeatedly). Low win rate can be profitable if the prices are big enough.

EV is what matters, not “how often you win.”

When EV isn’t enough

  • Variance: positive EV bets can lose for long stretches.
  • Bad estimates: EV depends on your probability estimate being realistic.
  • Line movement: a good bet at one price may be bad at another.

FAQ

What is a good EV in sports betting?

Any positive EV is good in theory, but in practice you want a meaningful edge after accounting for uncertainty and variance.

Does positive EV guarantee I’ll win money?

No. It means you made a good decision mathematically, but short-term outcomes can still lose due to variance.

How do I estimate win probability?

Use a model, sharp market signals, or disciplined handicapping. Start by converting odds to implied probability and then adjusting based on your analysis.

Related next steps