Position size calculator

How to calculate position size from a stop loss

Position sizing connects two decisions: the amount of account equity you choose to risk and the price distance between entry and stop. A wider stop uses more of that budget per share, so the same budget supports fewer shares.

Enter equity and prices in the same currency. The default 1% is an editable example, not a recommended allocation. CME’s position sizing lesson explains how a chosen risk limit and stop distance work together.

A 100 risk budget: 20 shares or 16 shares?

In the default example, account equity is 10,000 and the chosen risk budget is 1%, or 100. An entry of 100 and a stop of 95 put 5 of price risk on each share. The result is 20 shares, a position value of 2,000 and a planned price loss of 100.

Change only the stop to 94. Each share now uses 6 of the budget. With whole shares selected, the result becomes 16 shares: 96 of planned price loss and 4 unused. Choosing 0.01-share increments gives 16.66 shares, about 99.96 of planned price loss and 0.04 unused.

If the budget cannot cover even one selected increment, the calculator returns zero. It does not round up past the budget. A stop above entry uses the same distance formula and labels the calculation as short; that label does not establish borrowing availability.

A smaller stop can produce a much larger position

Keep the original inputs but move the stop to 99.50. The 0.50 distance produces 200 shares and a notional value of 20,000, twice the entered equity. The planned price loss is still 100. Risk budget and buying power measure different things.

Check broker limits separately. This tool uses linear share or asset-unit prices; futures multipliers, forex lots and options require different sizing inputs. Fees and slippage also sit outside the displayed price loss. As Investor.gov explains, a triggered stop order may execute at a different price.

Give the stop a reason before sizing the position

Start with the price level that would invalidate the setup, then calculate the quantity. The breakout and retest guide shows how a failed retest changes a chart scenario. Use the risk-reward calculator to compare that stop with a proposed target after costs.

After recording completed trades, you can review their average result after costs using the observed win rate and average winning and losing amounts. Keep those historical outcomes separate from the risk budget chosen for this position.