Risk-Based Position Size CalculatorFree online financial calculator — instant results, no sign-up
Size a long position from account risk and a stop price, excluding execution slippage.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Risk-Based Position Size Calculator
The Risk-Based Position Size Calculator sizes a long, whole-share position using your account equity, risk percentage, entry price, and stop price. It divides your dollar risk budget by the entry-to-stop distance and rounds down to whole shares. It also reports position notional and the estimated loss if those shares are sold exactly at the stop price, excluding execution slippage.
- Account equity ($)
- Your account's current equity in dollars, used as the base for the risk budget; the default is $50,000.
- Risk per trade (%)
- The percentage of account equity allocated to stop-based risk on this trade, entered as a percentage such as the default 1%.
- Entry price ($)
- The planned purchase price per share in dollars; the default is $100.
- Stop price ($)
- The planned stop price per share in dollars, which must be below the entry price for this long-position calculation; the default is $95.
Formula and method
B = A × (r / 100); d = E − S; Q = floor(B / d); N = Q × E; L = Q × d. With the defaults: B = 50000 × (1 / 100) = $500.00; d = 100 − 95 = $5.00 per share; Q = floor(500 / 5) = 100 shares; N = 100 × 100 = $10,000.00; L = 100 × 5 = $500.00.
- AAccount equity in dollars.
- rRisk per trade as a percentage, with 1 meaning 1%.
- BDollar risk budget for the trade.
- EEntry price in dollars per share.
- SStop price in dollars per share.
- dEntry-to-stop distance, or assumed loss in dollars per share.
- QWhole-share position size; floor means round down to the nearest whole number.
- NPosition notional in dollars at the entry price.
- LEstimated stop-based loss in dollars, assuming execution exactly at the stop price.
Multiply account equity by the risk percentage divided by 100 to obtain the risk budget. Subtract the stop price from the entry price to find risk per share, then divide the budget by that distance and round down to whole shares. Multiply the resulting share count by the entry price for notional and by the stop distance for stop-based loss. Use positive account equity and entry price, a nonnegative risk percentage, and a nonnegative stop price strictly below entry.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Account equity50000 $
- Risk per trade1 %
- Entry price100 $
- Stop price95 $
Results
- Risk budget$500.00
- Whole-share position100
- Position notional$10,000.00
- Stop-based loss$500.00
How to use the Risk-Based Position Size Calculator
- 1Enter your account equity in dollars; the default is $50,000.
- 2Enter your risk per trade as a percentage; the default 1% produces a $500.00 risk budget.
- 3Enter the planned entry price and a lower stop price; the defaults of $100 and $95 create a $5.00 per-share stop distance.
- 4Calculate the whole-share position; dividing $500.00 by $5.00 and rounding down gives 100 shares.
- 5Review the $10,000.00 position notional and $500.00 stop-based loss, then separately check buying power and execution risks.
Reading your result
Risk budget is the dollar amount allocated to this trade's modeled stop-based risk: $500.00 with the defaults. Whole-share position is the largest integer share count whose modeled loss does not exceed that budget: 100 shares. Position notional is the shares' purchase value at entry, not the amount at risk to the stop: $10,000.00. Stop-based loss is the estimated loss at the stated stop price: $500.00. Rounding down can make stop-based loss smaller than the risk budget.
Limitations
This calculation assumes a long position entered at the stated entry price and exited exactly at the stated stop price. It excludes execution slippage, commissions, fees, and taxes; gaps or poor liquidity can make actual losses exceed the risk budget, and a stop order does not guarantee its execution price. Sizing is based only on stop risk, with no cap for cash, buying power, leverage, or portfolio concentration. It uses whole shares and does not account for contract multipliers, short positions, or currency conversion. It does not determine whether the chosen stop or risk percentage is appropriate, and it is educational rather than personalized investment advice.
Common questions
Why does the default position have a $10,000.00 notional but only $500.00 of stop-based risk?+
The 100 shares cost $100 each, giving a $10,000.00 notional. The assumed loss is only the $5.00 difference between the $100 entry and $95 stop, multiplied by 100 shares, or $500.00; that estimate depends on exiting exactly at the stop.
Why must the stop price be below the entry price?+
This tool models a protective stop for a long position, so risk per share is entry minus stop. An equal stop produces division by zero, and a higher stop produces a negative distance that cannot be used for this sizing method.
Why round down, and can the result be zero shares?+
Rounding down keeps the modeled whole-share loss within the risk budget. If the risk budget is smaller than the entry-to-stop distance for one share, the result is zero shares. The default inputs divide evenly, so the result is exactly 100 shares.
Does the calculated share count guarantee affordability or limit my actual loss?+
No. The formula does not cap position notional at available cash or buying power, so affordability must be checked separately. It also excludes slippage: the default $500.00 stop-based loss is an estimate, not a guaranteed maximum.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.