Win Rate Is a Lie: Why Expected Value Is the Only Number That Matters

You can be right 70% of the time and still lose money. You can be wrong 70% of the time and still get rich. If that sounds backwards, stay with me — by the end you'll never look at your win rate the same way again.

Quick note before we start: this is educational commentary, not personalized financial advice. The goal here is to teach a way of thinking, not to tell you what to buy.

The number everyone obsesses over is the wrong one

Most retail traders fixate on win rate — the percentage of trades that made money. It feels like the scoreboard. It isn't. Win rate is one input. The number that actually decides whether you survive is expected value (EV): the average outcome of a bet if you could repeat it forever. EV combines how often you win with how much you win and how much you lose. Miss any one of those and you're flying blind.

Build it from scratch with a coin

A fair coin lands heads half the time. Suppose I pay you $11 on heads, and you pay me $10 on tails. Your win rate is exactly 50%. But your EV per flip is:

(0.5 × +$11) + (0.5 × −$10) = $5.50 − $5.00 = +$0.50

Same win rate as a coin flip, and you make money on every flip on average.

Now flip the payouts. You win $10 on heads, lose $11 on tails. Still a 50% win rate — identical hit rate. But now:

(0.5 × +$10) + (0.5 × −$11) = −$0.50

Same odds of being right, opposite destiny. Win rate told you nothing. The size of the wins versus the losses told you everything.

Push harder: the ugly win rate that gets rich

Roll one die. You only win on a six — a win rate of about 17%. Sounds terrible. But say you lose $1 on rolls of one through five, and win $10 on a six:

(5/6 × −$1) + (1/6 × +$10) = −$0.83 + $1.67 = +$0.84 per roll

You lose most of the time and you get richer.

This is exactly why a trend-following trader can lose on two-thirds of their trades and still crush it. Lots of small, controlled losses; occasionally a move that pays 10 or 20 times the risk. Ugly win rate, beautiful EV.

Meanwhile, the trader who wins nine times out of ten selling naked options and collecting tiny premiums looks like a genius — right up until one move wipes out a year of gains. High win rate, negative EV, hidden until the tail shows up.

The formula, in plain English

Expected value = (probability of winning × average win) − (probability of losing × average loss).

Four numbers, not one. Anytime someone brags about a win rate and leaves out the average win and average loss, they've shown you a quarter of the picture and asked you to bet on the whole thing.

How this connects to how markets price risk

When you buy a short-dated option, the market quotes you an implied probability and an implied payout at the same time. The premium is essentially the market's estimate of the bet's fair value plus a little edge for the seller.

Your job isn't to guess direction. Your job is to find spots where your estimate of the four numbers differs from the market's — and to act only when that difference is in your favor. That gap is your edge. No gap, no trade.

Positive EV isn't enough. You have to survive.

Positive expected value is necessary but not sufficient. You also have to survive long enough for the average to show up. Take our +$0.50 coin, but bet your entire account each flip. One bad run and you're at zero — and zero has no comeback. The math was right. The sizing killed you.

This is why disciplined traders risk a small, fixed fraction per trade — often something like 0.5% to 2% of the account. Not because it's a magic number, but because it keeps any single loss survivable, so positive expectancy has room to compound. Small size isn't timidity. It's the price of staying in the game long enough for your edge to pay you.

What a disciplined trader actually does

• Write down the four numbers before entering: rough probability, target win, defined loss. If you can't estimate them, that's a signal the trade is a guess, not a position.
• Demand positive EV, not comfort. Take the ugly 17% win rate if the payout justifies it.
• Size so ten losses in a row is annoying, not fatal.
• Judge yourself on process, not any single result. In the short run, even a great bet loses plenty.

The mindset shift

Stop asking, "Was I right?" Start asking, "Was that a good bet?" Being right is an outcome. Making a positive-EV bet, sized correctly, is a decision. You control the decision, not the outcome.

Over hundreds of trades, good decisions and bad luck converge toward your true edge. So do bad decisions and good luck — which is how the lucky eventually give it all back.

Run your own numbers. If the EV isn't there, the trade isn't there, no matter how confident you feel. That confidence is the most expensive number of all, and it never shows up in the math.

For the full walkthrough with every calculation on screen, watch the video: https://youtu.be/04xvX3GVBew