Expected value in one line
EV = probability × odds − 1. Above zero is a value bet, below zero is not.
Example. An outcome has a true probability of 50 %, so its fair odds are 2.00. A bookmaker offers 2.10.
0.50 × 2.10 − 1 = +5 %. On average you would expect 5 cents back per euro staked, over many such bets.
Most bets at most bookmakers have negative expected value, because the margin is built into the price. The same outcome at 1.90 gives 0.50 × 1.90 − 1 = −5 %.
Where the fair odds come from
The hard part is the probability. There are two ways to get it.
- Your own model. Works if it is better than the market. Few are, and you only find out by measuring it against the closing line.
- The market itself. Take the price of a sharp, low-margin bookmaker, remove the margin, and look for other bookmakers that still offer more. Our guide on fair odds shows the calculation.
The second way works because bookmakers do not all move at the same time. A sharp market moves first and others follow later, so for a while their prices can be too high.
How to tell whether it works
Do not judge a few dozen bets by profit. Measure closing line value: if your prices keep beating the fair close, the edge is real, whatever the last week looked like.
Expect long losing runs. At even odds, ten losses in a row start about once every 2,000 bets even with a coin that is perfectly fair. Stakes have to survive that. Many bettors stake a small, fixed share of their bankroll for that reason; only bet what you can afford to lose.
The traps that fake an edge
- Old prices. A fair price from an hour ago is not a fair price. Compare prices of the same moment.
- Different markets. Two-way including overtime is not the same as three-way in regular time, even when the screen shows the same teams. This is the most common source of huge fake values.
- Very high values. A value above roughly 15 % before kick-off in a major market is usually an error, a stale price or a different market. Check it before you believe it.
- Prices you cannot get. Odds can change between seeing and placing, and stakes can be capped.
- Bookmaker rules. Winning accounts get limited. Whether and how you use a bookmaker is your decision and your responsibility.
Value bets at Manometer
The board shows prices from more than 90 bookmakers against the Pinnacle fair price, if you want to bet yourself. The Manometer Agent places bets automatically on your own accounts, if you do not. How it works explains the whole pipeline.
Next: How to calculate fair odds. Past results do not predict future results. Betting is for adults only and can be addictive: responsible betting.