Trading glossary
Position sizing is deciding how much to allocate to a single trade based on risk. Learn common approaches and why it is central to risk management.
Position sizing is the decision of how large a single trade should be. Rather than choosing an amount arbitrarily, many traders size a position around how much they are willing to risk if the trade goes against them. The goal is to keep any one loss within limits the trader has set in advance, so a single trade cannot cause outsized damage.
A widely discussed method ties size to a fixed percentage of account value risked per trade, combined with the distance to a stop-loss. If a trader risks a small percentage per trade, the stop distance determines how many units the position can hold. Other approaches use fixed dollar amounts or volatility-based sizing, adjusting size when a market is more or less volatile.
Position sizing links a strategy's edge to survival, because even a sound approach can face a long losing streak. Sizing that ignores risk can lead to a deep drawdown from just a few bad trades. It works together with the risk-reward ratio and stop-loss placement. This is educational information, not personalized advice, and trading involves the risk of loss of capital.
A common method risks a small, fixed percentage of the account per trade and uses the distance to the stop-loss to determine how many units to hold, keeping any single loss within a set limit.
It controls how much a single losing trade can affect an account. Poor sizing can produce large drawdowns from a few bad trades, even when the underlying strategy is reasonable.
The distance between entry and stop-loss defines the per-unit risk. Combined with the amount a trader is willing to risk, that distance determines how large the position can be.