Enter the decimal odds, your estimated probability of winning, and optionally your stake to calculate the expected value of your bet.
Calculation Result
Expected Value:
Expected Value %:
A positive EV means the price is bigger than your estimated probability justifies. Betting only positive-EV spots won't win every bet, but over hundreds of bets the average converges towards the EV shown.
Bookmakers price markets with a margin, so the average bet has negative EV by design. To profit you must find the exceptions — outcomes the market has underpriced. An EV calculator turns that search into arithmetic: it tells you exactly how much value your probability estimate implies at the offered odds, and how big your edge is.
How Expected Value is calculated
EV = (Probability × Odds − 1) × Stake. The bracket is your edge per unit: probability × odds is your expected return per 1.00 staked, and subtracting 1 removes the stake. EV% = (Probability × Odds − 1) × 100 expresses the same thing per hundred. Break-even sits exactly where your probability equals 1 ÷ odds — anything above is value, anything below is the bookmaker's edge.
Why use an EV calculator?
It replaces emotion with arithmetic — a bet either clears the value bar or it doesn't, whatever your feelings about the teams.
It quantifies your edge, letting you compare opportunities across markets and pick the strongest — and it feeds directly into staking methods like the Kelly criterion.
It filters out negative-EV bets, which is where most long-term losses actually come from.
Common mistakes when calculating EV
Overconfident probabilities: if your '60%' outcomes only win 52% of the time, every EV figure you compute is fiction. Calibrate against results.
Comparing your estimate against raw implied probability without stripping the margin — a 105% market makes every price look closer to fair than it is.
Judging the method by a week of results: EV is a long-run average, and short-term variance will swamp a few percent of edge over small samples.
Worked Examples
Identifying a Positive EV Bet
A bookmaker offers odds of 2.50 on a football team to win. Your analysis suggests this team has a 45% probability of winning. Enter odds 2.50, probability 45%, and stake £100. The calculator shows an expected value of +£12.50 per bet (EV% = +12.5%). This means that over many identical bets, you'd expect to profit £12.50 for every £100 staked — a strong positive expected value that makes this bet worth taking long-term.
Spotting a Negative EV Bet
A bookmaker offers odds of 1.80 on a tennis player to win a set. You believe the true probability is 50%. Enter odds 1.80, probability 50%, and stake €50. The calculator shows an expected value of -€5.00 per bet (EV% = -10%). Despite a coin-flip probability, the odds don't compensate enough — you'd lose €5 on average for every €50 staked. This is a bet to avoid regardless of how confident you feel about the outcome.
Comparing Markets for Best Value
You estimate a boxer has a 40% chance of winning. Bookmaker A offers odds of 2.80, while Bookmaker B offers 2.40. For Bookmaker A: EV = (0.40 × 1.80) - (0.60 × 1.00) = +12%, a profitable bet. For Bookmaker B: EV = (0.40 × 1.40) - (0.60 × 1.00) = -4%, a losing proposition. Same event, same probability estimate, but one is +EV and the other is -EV. Always compare odds across bookmakers before placing your bet.
A value bet is one where the odds pay more than the outcome's true probability justifies — equivalently, where your estimated probability beats the bookmaker's implied probability (1 ÷ decimal odds). If you make an outcome 50% likely and the price is 2.20 (implied 45.5%), the bet has positive expected value even though it loses half the time.
Build estimates from evidence: recent form weighted by opponent strength, head-to-head data, injuries and motivation, plus statistical models where you have them. Two practical checks help: strip the bookmaker margin from market prices to see the market's real opinion, and track your estimates against outcomes over time — persistent bias means your process needs recalibrating.
Yes, and regularly. Positive EV describes the average, not any single result — a +10% EV bet at 2.50 still loses 55% of the time. Profitability emerges over large samples, and losing streaks of ten or more bets are statistically normal. This is why bankroll management matters as much as bet selection.
How this calculator works
Formula:
EV = (p × odds − 1) × stake
Worked example:
p = 0.60, odds = 2.0, stake = 100 → EV = (1.2 − 1) × 100 = +20
