Stock Position Sizing Methods
Position sizing determines how much exposure a portfolio takes to a security or trade. It links an explicit risk budget to price distance, concentration, liquidity and the investor’s ability to bear loss.
How it works
For an illustrative stop-distance rule, shares=floor(planned cash loss/(entry−stop)) for a long position when the distance is positive. Add a cost and slippage allowance where appropriate. This is a planning model, not proof the stop will execute as intended. Also cap position value and aggregate correlated exposures.
Worked example
An account of 20,000 chooses a fictional planned loss budget of 100, with entry 50 and stop reference 48. Ignoring costs, 100/2=50 shares, a 2,500 position. If an earnings gap causes a fill at 44, the loss is 50×6=300 before fees: three times the plan.
Amounts, prices and scenarios are fictional teaching examples. They exclude any effects not explicitly stated and are not trade recommendations.
Limits and common mistakes
Sizing by a tight stop can create a large position whose gap exposure is unacceptable. Leverage, market closures and liquidity matter. Percentages that suit one account do not establish a universally appropriate risk recommendation.
Knowledge check
Does a 0.5% planned risk mean the position itself is only 0.5% of the account?
Read the explanation
No. Planned loss and position market value are different. In the example, the loss budget is 0.5% but the position value is 12.5%.
References and further reading
- SEC Investor.gov: stocks, ownership and risks
- SEC: company filings and financial reports
- SEC: beginners’ guide to financial statements
These sources explain the underlying concepts and specifications. They do not endorse QBMFX Academy. Check the relevant market, protocol version and reporting rules before applying an example.