Position Sizing Calculator
Trade position sizing.
Calculate the optimal position size for a trade based on account size, risk-per-trade percentage, and your stop-loss distance.
What this tool does
Position size for a trade depends on account size, the percentage of capital you're willing to risk per trade, and the distance between your entry price and stop-loss level. This calculator takes those four inputs and returns the number of shares or contracts you could hold at that position size. The result shows how many units align your actual loss—if the trade hits your stop-loss—with your target risk percentage. Account size and risk percentage have the strongest influence on the outcome; wider stop-loss distances reduce position size proportionally. A typical use case is planning entry and exit points before opening a position. The calculator assumes your stop-loss executes at the specified price and doesn't account for slippage, trading costs, or margin requirements. The result is for educational illustration of position sizing mechanics.
Quick answer: with the default values, the result is 200 shares (Position Size). Adjust the values below for your own figures.
Enter Values
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Formula Used
Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Position sizing calculator determines how many shares/contracts to trade based on account size, risk tolerance, and stop loss distance. The fundamental formula: position size = (account × risk %) / (entry - stop). Most professional traders risk 1-2% per trade. 100k account × 1% = 1,000 max risk per trade.
Example: 100k account, 1% risk per trade = 1,000 risk. Stock entry 50, stop 45 = 5 risk per share. Position size = 1,000 / 5 = 200 shares. Position value = 10,000 (10% of account). If stopped out: lose 1,000 (1% of account). If 2x reward target: gain 2,000 (2% of account, 2:1 reward/risk).
Position sizing math: at 1% risk per trade it takes roughly 100 consecutive losses to reach near-total drawdown, about 50 at 2% risk, and about 20 at 5% risk (a losing streak that grows far more likely as risk rises). Bigger position sizes amplify both gains and drawdowns, and a common convention is to keep risk at or below 2% per trade. Position size can be aligned with the strategy's win rate and reward/risk profile.
A worked example
With the defaults: account size of 100,000, risk per trade of 1%, entry price of 50, stop loss price of 45. The tool returns 200 shares. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.
What moves the number most
The result responds to Account Size, Risk Per Trade %, Entry Price, and Stop Loss Price. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.
The formula behind this
Position size = (account × risk %) / (entry price - stop loss). Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.
Using this well
What this doesn't capture
This is a simplified model that holds its assumptions constant. Real outcomes vary with market conditions, costs, taxes, and timing, so the figure is best read as one scenario rather than a forecast.
£100,000 × 1% / (£50-£45) = 200 shares.
Inputs
| Position Value | $10,000.00 |
|---|---|
| Risk Amount | $1,000.00 |
| Risk per Share | $5.00 |
| Position % of Account | 10.00% |
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
This calculator computes position size by dividing the amount of capital at risk by the price distance between entry and stop-loss levels. It first multiplies your account size by your chosen risk percentage to determine the absolute amount of capital you are willing to risk on the trade. It then calculates the difference between your entry price and stop-loss price, which represents the per-unit price movement at which the position would be closed. The position size is derived by dividing the total risk amount by this per-unit risk amount. The calculator assumes a linear relationship between account size, risk allocation, and position sizing. It does not model trading costs, slippage, tax implications, market liquidity constraints, or the probability of reaching the stop-loss level.
References
Frequently Asked Questions
What % risk per trade?
Account size and position?
Stop loss placement?
Reward/risk ratio?
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