🎯 In 30 seconds: Losses and gains are not symmetrical. Lose 10% and you need 11.1% to get back to even. Lose 50% and you need 100%. That one fact is why professional traders think about how much they can lose before they think about how much they can make. The usual answer is to risk a small, fixed slice of the account on each trade, often 1% or 2%, so that a run of losses hurts but never ends the game.
Why this chapter comes before any strategy
Most people start trading by asking "what should I buy?" That is the wrong first question. The first question is "how much can I lose on this, and can I live with it?"
The reason is simple. No strategy wins every time. Even a good one has losing weeks and losing months. If one bad stretch wipes you out, you never get to the good stretch that follows.
The evidence on short-term trading is also sobering. A study of everyone who started day trading Brazilian index futures from 2013 to 2015 and kept going for at least 300 days found that 97% of them lost money. Only 0.4% earned more than a bank teller's wage. Another long-running line of research on US brokerage accounts found that the households that traded the most earned 11.4% a year while the market returned 17.9%. You will see these studies again in Investing vs trading.
None of this means you cannot learn to trade. It means the default outcome is losing, and the first job is to keep losses small while you find out whether you have any skill at all.
The math of losses
Here is the key idea. When you lose money, you have a smaller amount left to grow. So the gain you need to recover is always bigger than the loss you took.
The formula is short:
gain needed = loss / (1 - loss)
Write the loss as a decimal. A 20% loss is 0.20, so the gain needed is 0.20 / 0.80 = 0.25, or 25%.
Check it with dollars. You start with $10,000 and lose 20%. You now have $8,000. To get back to $10,000 you need $2,000 more, and $2,000 is 25% of $8,000.
| Loss | What $10,000 becomes | Gain needed to get back to $10,000 |
|---|---|---|
| 5% | $9,500 | 5.26% |
| 10% | $9,000 | 11.11% |
| 20% | $8,000 | 25% |
| 25% | $7,500 | 33.33% |
| 30% | $7,000 | 42.86% |
| 40% | $6,000 | 66.67% |
| 50% | $5,000 | 100% |
| 60% | $4,000 | 150% |
| 75% | $2,500 | 300% |
| 90% | $1,000 | 900% |
Notice the shape. Small losses are cheap to fix. Big losses are not. Going from a 50% loss to even means doubling your money, something a broad stock index has historically taken years to do.
The same math explains why a +50% month followed by a -50% month leaves you down, not flat. $10,000 becomes $15,000, then $7,500. You are down 25% even though the two percentages "cancel out".
What a run of losses does to you
Losing streaks are normal. With a strategy that wins half the time, the chance of at least five losses in a row somewhere in 100 trades is about 81%. Drawdowns and losing streaks has the full table.
So the useful question is: what does a streak do to your account at different risk levels? Risk per trade here means the amount you lose if the trade hits your exit point, as a percentage of your whole account.
| Risk per trade | After 5 losses in a row | After 10 | After 20 |
|---|---|---|---|
| 0.5% | $9,752 | $9,511 | $9,046 |
| 1% | $9,510 | $9,044 | $8,179 |
| 2% | $9,039 | $8,171 | $6,676 |
| 5% | $7,738 | $5,987 | $3,585 |
| 10% | $5,905 | $3,487 | $1,216 |
| 25% | $2,373 | $563 | $32 |
All figures start from $10,000 and assume each loss is the stated percentage of what is left. That is why the numbers shrink a little more slowly than simple subtraction would suggest.
At 1% risk, ten straight losses cost you about 9.6%. That stings, but it is recoverable with a 10.6% gain. At 10% risk, ten straight losses cost you 65%, and you need a gain of almost 187% to recover.
Risk of ruin
Risk of ruin is the chance that your account falls so far that you cannot or will not keep trading. Some people define ruin as zero. A more practical line is losing half your starting money, because very few people keep following their plan after that.
Here is a rough count of how many losses in a row it takes to cut an account in half at each risk level:
| Risk 1% per trade | 69 losses in a row |
| Risk 2% per trade | 35 losses in a row |
| Risk 5% per trade | 14 losses in a row |
| Risk 10% per trade | 7 losses in a row |
| Risk 25% per trade | 3 losses in a row |
Of course, losses do not always come in one unbroken run. So the better test is to calculate the full probability. The table below does that for 200 trades. It shows the chance that the account drops to half its starting value at any point along the way.
| Risk per trade | System with an edge: wins 45%, wins are 2x losses | System with no edge: wins 50%, wins equal losses |
|---|---|---|
| 1% | under 0.01% | under 0.01% |
| 2% | under 0.01% | 1.9% |
| 5% | 1.5% | 43.2% |
| 10% | 16.0% | 80.3% |
| 20% | 52.7% | 97.3% |
These are exact calculations for hypothetical systems, not market data. Two lessons stand out.
- A real edge does not save you from oversizing. The first system makes money on average. Risk 20% per trade with it and you still have a better than even chance of losing half your account within 200 trades.
- Small risk buys you time when you have no edge. Most beginners do not yet know whether they have an edge. At 1% to 2% risk, a no-edge trader is very unlikely to be cut in half in 200 trades, which leaves time to learn, review and stop if the results are not there.
The 1% and 2% rules
The 1% rule says: never risk more than 1% of your account on a single trade. The 2% rule is the same idea with a 2% cap. Many beginners do well to start at 0.5% or 1%.
This is the most misunderstood rule in trading. It does not mean you only put 1% of your money into a trade. It means the loss, if your exit is hit, should be no more than 1% of the account.
A worked example with hypothetical numbers:
| Account | $10,000 |
| 1% risk budget | $100 |
| Buy price | $50.00 |
| Exit if wrong (stop) | $47.00 |
| Risk per share | $3.00 |
| Shares: $100 / $3 | 33 (rounded down) |
| Money in the trade | $1,650 |
| Planned loss if the stop is hit | $99, about 1% |
You put $1,650 to work, but you only planned to lose $99. The full method, with more examples, is in Position sizing. Where to put that $47 exit is covered in Stop losses.
One honest caveat: a stop is a plan, not a guarantee. If a stock opens far below your stop after bad news, you can lose more than 1%. The SEC's investor bulletin on stop orders says the price you get "can deviate significantly" from the stop price. That is one more reason to keep the planned risk small.
Why survival beats brilliance
A trader who makes 40% one year and loses 50% the next ends up down 30%. A trader who makes 8% two years in a row ends up up 16.6%. The second trader never had a headline year and still came out far ahead.
That is the pattern you see again and again. The traders who last are rarely the ones with the biggest wins. They are the ones whose losses stay small enough to recover from.
Risk control also protects your thinking. A loss of 1% is easy to accept and move on from. A loss of 20% in a day makes most people panic, freeze or try to "win it back" with an even bigger bet. Trading psychology covers why.
There are other risks outside any single trade too: the whole market can fall at once, trading costs add up, and borrowed money can make losses bigger than your deposit. Investor.gov notes that leveraged trading can lose "substantially more" than you put in. See Margin before you ever borrow to trade.
Try it
Open the paper portfolio and set a pretend account size, say $10,000. For your next five practice trades, write the entry, stop and share count before you click, using the 1% rule. After each trade, check: did the loss, if any, stay near $100? If it did not, write down why (a gap, a moved stop, too many shares). Then take the recovery table above and work out by hand what gain you need after a 15% loss and a 35% loss. You should get 17.65% and 53.85%.
- After a 15% loss, what gain do you need to get back to even? Answer: About 17.65% (0.15 / 0.85).
- $10,000 gains 50% one month and loses 50% the next. Where do you end up? Answer: At $7,500, down 25%. The percentages do not cancel out.
- What does the 1% rule actually mean? Answer: The loss if your exit is hit should be no more than 1% of the account. It does not mean you put only 1% of your money into the trade.
- Your account is $10,000 and you follow the 1% rule. You buy at $50.00 with a stop at $47.00. How many shares, and how much money is in the trade? Answer: 33 shares ($100 / $3, rounded down), about $1,650 in the trade, with a planned loss of $99.
Sources
- Chague, De-Losso and Giovannetti (FGV EESP, 2020): Day trading for a living?
- Barber and Odean, Journal of Finance (2000): Trading is hazardous to your wealth
- Investor.gov (SEC): Investor bulletin, stop, stop-limit and trailing stop orders
- Investor.gov (SEC): Thinking of day trading? Know the risks
- Investor.gov (SEC): What is risk?