Position sizing

Most traders focus on entries: where to buy, where to sell, which pattern to trust. Few focus on size. This is a mistake. A trader with an 80% win rate who sizes too large will eventually hit a losing streak that wipes out the account. A trader with a 45% win rate who sizes correctly can survive long enough for their edge to play out.

Position sizing is what separates the trader who survives bad weeks from the trader who does not.

Position sizing is what separates the trader who survives bad weeks from the trader who does not.

The most widely used approach is the percent-risk rule. The trader decides in advance what percentage of the account they are willing to lose on any single trade, then sizes the position so that the stop loss equals that amount. Common figures are 1% per trade for conservative traders, 2% for moderate, and rarely above 3% for any retail trader. A 1% rule means that even a string of ten consecutive losses, which is rare but not impossible, costs roughly 10% of the account, not the whole thing.

Position size is calculated using three inputs: account size, percent risk per trade, and the distance from entry to stop loss measured in pips.

The formula: position size (in lots) = (account size x percent risk) divided by (stop loss in pips x pip value per lot).

Worked example: a $10,000 account, risking 1% per trade ($100), with a 50-pip stop on EUR/USD where the pip value per standard lot is approximately $10.

Position size = $100 divided by (50 x $10) = 0.2 lots, or two mini lots.

If the trade hits the stop, the loss is $100. If the same trader took a 100-pip stop with the same 1% risk, the position size would be 0.1 lots. Wider stops require smaller positions.

New traders often pick a position size based on what feels reasonable, like 1 lot, and apply it to every trade regardless of stop distance. This is the wrong way around. Position size should be calculated from the stop, not chosen in advance. The same 1-lot position can risk $100 with a 10-pip stop or $500 with a 50-pip stop. Without sizing relative to risk, the trader has no control over how much each trade actually costs.

Pick your percent-risk before placing the trade, not after. Calculate position size based on the stop loss. Avoid changing the rule trade-by-trade. Avoid the temptation to size up after a winning streak or down after a losing one. Consistency is the point. The rule only works if it is followed every time.