Free tool
Expected value calculator.
Value is the whole game: is the price longer than the true chance deserves? This turns your probability estimate and the odds into the one number that answers it — honestly, in both directions.
EV is only as honest as your probability. The market's implied probability is a fact; your estimate is an opinion. A positive number here means value if your opinion is better than the market's — and it doesn't promise the next bet wins. Over-rate your own read and the EV is fiction. 18+ · information, not advice.
The worked example
A £10 bet at 3.0 with a 40% estimated chance: EV = £10 × (0.40 × 3.0 − 1) = +£2.00, or +20% of stake. The price of 3.0 implies just 33.3%, so your edge is 40% − 33.3% = 6.7 points. Trust that estimate and it's a value bet; drop it to 33.3% and the EV is exactly zero — you'd just be paying the fair price.
Straight answers
What is expected value in betting?
Expected value (EV) is the average result of a bet if it were repeated many times. A positive EV means the price is longer than the true chance deserves; a negative EV means you're paying the bookmaker's margin. It's the single number that separates a value bet from a mug bet.
How do you calculate expected value?
EV per £1 staked = (your estimated probability × decimal odds) − 1. Multiply by your stake for the £ figure. If your 40% chance is priced at 3.0, EV = 0.40 × 3.0 − 1 = +0.20, or +20% — a value bet, if your estimate is right.
What is a good expected value for a bet?
Any positive EV is, in theory, a bet worth making repeatedly; the bigger the number, the bigger the edge. But EV is entirely dependent on your probability estimate being accurate — a confidently wrong estimate produces a confidently wrong EV.
Does positive EV mean I will win?
No. Positive EV means the bet wins on average over a large sample; any single bet can still lose, and a run of them can lose. EV is a long-run expectation, not a prediction of the next result — which is exactly why bankroll and variance matter.
Computing EV is arithmetic. Estimating a probability better than the market is the edge.
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18+ · Education, not betting advice · No tips, no picks · BeGambleAware.org
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