Most traders who blow up their accounts do not do it with one spectacular bet. They do it with a string of losses that were each a little too big. The risk-per-trade rule exists to stop that happening. It is simple, unglamorous and probably the single most important habit a new trader can build.
What the rule is
A risk-per-trade rule sets the maximum amount of your account you are willing to lose on any one trade. Many traders use a figure between half a per cent and 2 per cent. So with a 10,000 pound account and a 1 per cent rule, the most you would accept losing on a single trade is 100 pounds.
The key word is lose. The rule is not about how much you put into a trade, but how much you stand to lose if your stop loss is hit.
How it works in practice
First you decide where your stop loss goes, based on the chart or your reasons for the trade, not on how much you want to make. Then you work out your position size so that, if the price reaches that stop, you lose no more than your set amount. If the stop needs to be far away, the position has to be smaller. If it can be close, the position can be larger.
Our guide to position sizing walks through the calculation step by step.
Why it matters so much
The maths of losses is unforgiving. If you lose 10 per cent of your account, you need an 11 per cent gain to get back to where you started. Lose 50 per cent and you need to double your money. Small, controlled losses keep you in the game long enough for your strategy to work.
Even a good strategy will have losing streaks. With a 1 per cent rule, ten losses in a row would cost you roughly a tenth of your account, painful but survivable. With a 10 per cent rule, the same run could wipe out most of it.
The psychological benefit
Knowing exactly what you can lose before you enter a trade removes a lot of stress. It makes it easier to stick to your plan, accept losses calmly and avoid the temptation to move your stop or double down. It also helps on big news days, when prices can jump suddenly. Our guide to trading the knee-jerk reaction explains why those moments are especially dangerous.
Common mistakes
Beginners often break the rule after a loss, taking a bigger position to win the money back quickly. Others ignore it when they feel very confident about a trade. Some forget that several trades on related markets, such as different oil companies, can add up to one large bet. The rule only works if it applies every time.
The bottom line
A risk-per-trade rule caps how much any single trade can hurt you. It will not make a bad strategy profitable, but it will give a good one the time it needs to work.
Risk management is where most traders succeed or fail. If you want an honest look at how you manage yours, take the free Samuel & Co Trading Trader Assessment.
