For bettors

Expected value of a bet

If you could place this exact bet a thousand times, what would you make on average? Enter the price and your own probability estimate.

Inputs

Stake

Decimal odds offered

Your estimated win probability50%

The offered price implies 45.5%. A bet is +EV only when your estimate beats that.

Result

Expected value

—

EV % of stake

—

Your edge over the price—

Break-even probability—

Fair odds for your probability—

EV is only as good as your probability estimate — and a single bet still wins or loses in full. Positive EV pays off over a large sample, not on any one wager.

What expected value tells you

Expected value (EV) is the average result of a bet if you could repeat it forever. A bet wins the stake × (odds − 1) with probability p and loses the stake with probability 1 − p, so EV = p × stake × (odds − 1) − (1 − p) × stake. A positive number means the bet makes money on average; a negative number means it loses on average, however it turns out this once.

The whole thing rests on your probability

The odds come from the bookmaker; the probability p is your estimate, and the calculator only reflects it back. If you enter 55% and the true chance is 48%, the tool will report a healthy edge that does not exist. Good probability estimates come from a model, a market you know well, or a sharper book's price — not from how confident a bet feels.

Break-even and edge

The break-even win rate for a price is 1 ÷ decimal odds — 50% at 2.00, 40% at 2.50. Your edge is your probability minus that figure. A 2–4 point edge is already meaningful over a season; anything above about 10 points usually means the price is stale, the market is different from what you think, or your estimate is off.

Frequently asked questions

How is expected value of a bet calculated?

EV = p × (stake × (odds − 1)) − (1 − p) × stake, where p is your estimated win probability. Positive EV means the bet wins on average over many repeats.

What win rate do I need to break even?

1 ÷ decimal odds. At 2.00 you need to win more than 50% of the time; at 1.50, more than 66.7%.

If a bet is +EV, will I win it?

Not necessarily. A single bet still wins or loses in full. Positive EV pays off across a large sample, not on any one wager.

Where should my probability estimate come from?

A statistical model, a market you genuinely understand, or the price at a sharp bookmaker or exchange with the margin removed. The no-vig price from a market leader is the most common reference for recreational bettors.

How do I strip the margin from a bookmaker price to get a fair probability?

Take the implied probabilities of every outcome (1 ÷ odds), add them up, and divide each one by that sum. The result is the no-vig probability. Our bookmaker margin / vig remover does this in one step.

Does a +EV bet mean I should stake more on it?

Only up to a point. A bigger edge justifies a bigger stake, but past a sensible fraction of your bankroll the risk of a losing run outweighs the growth. The Kelly criterion calculator turns your edge into a stake size and most people use a half or quarter of it.

Does EV account for bookmaker limits or account restrictions?

No. It assumes you can place the stake you want at the price shown. In practice a consistently +EV bettor gets stake limits reduced, which is a real constraint the number does not capture.

Can expected value be positive on a losing bet?

Yes, and that is the point. EV is about the decision, not the outcome. A +EV bet that loses was still the right bet; a −EV bet that wins was still the wrong one. Judge your process over hundreds of bets, not the last result.

All tools →