Expected Value in Betting, Explained
Expected value is the one idea that separates betting with an edge from betting on a hunch. It is simple arithmetic, it has nothing to do with how often you win, and it is the only sensible way to judge a record, including the one on this site.
Odds are probabilities in disguise
Decimal odds tell you what you get back per unit staked, winnings and stake together. Turn them upside down and they tell you something more useful: the chance the price implies. Divide 1 by the odds. A price of 2.00 says the bookmaker rates the outcome a 50% chance. A price of 1.50 says 66.7%. A price of 4.00 says 25%.
Add up the implied chances of every outcome of one match and you get more than 100%, because every price is shaded in the bookmaker's favour. That excess, usually 2% to 8% on a main market, is the margin. It is the reason that betting at random loses money over time even when the odds look fair.
What expected value is
The expected value of a bet is what it is worth on average, per unit staked, if you could place it many times. Multiply the true chance of winning by the profit if it wins, subtract the chance of losing multiplied by the stake. At odds of 2.00 and a true chance of 55%: 0.55 × 1 − 0.45 × 1 = +0.10 units. The same selection at a true chance of 45% is worth −0.10 units. The price has not changed. The judgement of the probability has.
A bet has positive expected value when its true probability is higher than the implied probability of the price. That is the whole game. A bettor with an edge is one who, over a large number of bets, is right about probabilities more often than the prices are.
Why strike rate alone misleads
A 70% strike rate sounds excellent. At average odds of 1.30 it loses money, because break-even at 1.30 is 76.9%. A 35% strike rate sounds dreadful. At average odds of 3.20 it is a profit of 12% on stakes. The strike rate is only meaningful beside the prices, which is why every table on this site shows the odds and the implied strike rate next to the actual one.
Reading it off a real record
Clarity Tip's record is a worked example. Across 4,865 settled tips at an average price of 2.19, the prices implied a strike rate of 54.0%. The actual strike rate is 55.4%, a gap of +1.4 points.
The same thing measured in money: 4,865 units staked returned 5,058.5 units, a profit of +193.4 units and a return on stakes of +4.0%. That return is the realised expected value per unit, +0.0 units for every unit staked, averaged over the whole record.
A positive gap over this many tips is what an edge looks like in the data. It is not proof of one, because a sample this size can still carry a couple of points of luck either way, but it is the right thing to measure. The odds ranges and markets guides make the same measurement band by band and market by market, where it is more informative than the overall figure.
What expected value cannot tell you
It cannot tell you what will happen to a single bet, or to the next ten. A positive expected value bet loses all the time; that is what the odds mean. It also says nothing about how bumpy the road is. Two records with the same return can have very different losing runs, and the losing runs guide is the place for that. Lastly, past expected value is an estimate of future expected value, not a guarantee of it. Markets change, and so do the people pricing them.
The odds used throughout are the prices recorded when each tip was published. The closing line value guide covers what happens to those prices before kick-off and why it matters.
Frequently asked questions
What is a positive expected value bet?
A bet whose true chance of winning is higher than the chance the odds imply. At decimal odds of 2.00 the implied chance is 50%; if the selection really wins 55% of the time, each unit staked is worth 1.10 units on average and the bet has a positive expected value of +0.10 units. It can still lose, and often will. EV describes the average over many bets, not any single one.
How do I convert odds to implied probability?
Divide 1 by the decimal odds. 1.50 implies 66.7%, 2.00 implies 50%, 3.00 implies 33.3%, 5.00 implies 20%. For fractional odds, convert to decimal first by adding 1 (so 5/2 is 3.50). Bookmakers' prices on all outcomes of one event add up to more than 100%; the excess is their margin.
Can expected value be read off a tipster's record?
Approximately, yes. Return on stakes over a large number of tips is the realised expected value per unit. The strike rate minus the average implied probability, measured over the same tips, says whether the prices were beaten. Both need a large sample before they mean much; a few hundred tips can show a positive figure by luck alone.
More guides
- Which Odds Ranges Win Most Often · Strike rate and return for every price band in the record, against what the odds implied.
- Results by Betting Market · Match winner, totals, handicaps, both teams to score and props: how each market has performed.
- How Long Losing Runs Last · The longest winning and losing runs in the record, the biggest drawdown, and what that means for a bankroll.
- Staking Plans: Flat, Percentage and Kelly · How the main staking methods behave through a losing run, with the record's own drawdown as the test case.
- Closing Line Value and Why Odds Move · Why the price at kick-off matters, how to measure whether you beat it, and what it can and cannot tell you.
- All guides and monthly results
18+ only. Please gamble responsibly. Past results do not guarantee future outcomes. Figures on this page are recomputed from the public record as tips settle.