Position Size Calculator
Calculate exact share count based on your portfolio size, risk tolerance, and stop-loss level. Free position size calculator for disciplined risk management.
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How It Works
Enter your total portfolio value, the percentage of capital you are willing to risk on this trade, the entry price, and your stop loss price. The tool calculates the exact number of shares to buy, the total position cost, and the dollar amount at risk. This ensures your position size is always aligned with your risk tolerance, not your conviction level. One hundred thousand portfolio at one percent risk budgets one thousand dollars loss per trade maximum. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position. Position cost ten thousand can coexist with one thousand risk when stop defines loss cap not capital deployed.
Position sizing is the single most important risk management rule in trading. Even a strategy with a 60% win rate will eventually experience a long string of losses, and without disciplined sizing, a single large position can wipe out months of gains. By always calculating position size from your risk budget rather than guessing a dollar amount to invest, you ensure that no single trade can end your trading career. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position. Position cost ten thousand can coexist with one thousand risk when stop defines loss cap not capital deployed.
Disciplined position sizing protects your portfolio from catastrophic drawdowns. By fixing risk per trade as a percentage of capital, you absorb losing streaks without emotional decisions. This free position size calculator does the math instantly so you focus on strategy, not arithmetic.
Use Position Sizing Calculator whenever inputs change: after market moves, new contributions, or revised personal assumptions. Bookmark the page for quick reruns without installing software.
Step by step
- Open Position Sizing Calculator and enter your current inputs.
- Review calculated outputs and summary tables.
- Adjust assumptions and compare scenarios side by side.
Worked example
Example scenario for Position Sizing Calculator: 60%. Enter those values above to reproduce the walkthrough described in How it works.
Adjust one input at a time to see sensitivity. Position Sizing Calculator updates instantly so you can stress test optimistic and conservative assumptions before acting.
When to use this calculator
Reach for Position Sizing Calculator when calculate the exact number of shares to buy based on your portfolio size, risk tolerance, and stop-loss level.. It suits quick what if analysis before trades, allocation changes, or plan updates.
Pair with related tools when the decision spans taxes, liquidity, or multi year projections beyond what one formula captures.
Common mistakes
Copying outputs without checking input units or stale market prices is a frequent error with Position Sizing Calculator. Confirm tickers, percentages, and dates before acting.
Running a single baseline scenario ignores tail risks. Stress test with conservative inputs and compare against related tools listed below when the decision is material.
The Formula
riskBudget = portfolioValue × (riskPct / 100)
riskPerShare = |entryPrice - stopLossPrice|
sharesToBuy = floor(riskBudget / riskPerShare)
positionCost = sharesToBuy × entryPrice
riskAmount = sharesToBuy × riskPerShare
Risk per share uses absolute difference between entry and stop loss. Floor ensures whole shares only. One hundred thousand portfolio at one percent risk budgets one thousand dollars loss per trade maximum. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position. Position cost ten thousand can coexist with one thousand risk when stop defines loss cap not capital deployed.
Limitations and assumptions
Risk per share uses absolute difference between entry and stop loss. Floor ensures whole shares only. One hundred thousand portfolio at one percent risk budgets one thousand dollars loss per trade maximum. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position. Position cost ten thousand can coexist with one thousand risk when stop defines loss cap not capital deployed. Position Sizing Calculator does not replace personalized advice. Fees, slippage, account specific rules, and behavioral constraints may change real world outcomes.
Key terms
- What is position sizing in trading
- Position sizing is the process of determining how many shares of a stock to buy based on how much money you are willing to lose if the trade goes against you.
- How is position size calculated
- The formula is: sharesToBuy = riskBudget / riskPerShare, where riskBudget = portfolioValue times (riskPct / 100) and riskPerShare = entryPrice stopLossPrice.
- Model assumption
- The common rule among professional traders is to risk no more than 1% to 2% of your portfolio per trade.
Compare alternatives
Use with the Risk to Reward Ratio Evaluator to assess trade quality, or the Trailing Stop Loss Router for dynamic stop management. Use those calculators when position sizing calculator alone does not capture the full decision.
Internal links on portfolios.tools help you chain calculators: run Position Sizing Calculator first, then validate edge cases with a specialized tool from the related section below.
FAQ
What is position sizing in trading?
Position sizing is the process of determining how many shares of a stock to buy based on how much money you are willing to lose if the trade goes against you. Instead of investing a fixed dollar amount, you calculate the maximum risk per trade as a percentage of your portfolio, then divide that risk budget by the per share risk (the distance between your entry and stop loss). This ensures no single trade can devastate your portfolio. Never widen stop after entry; resize before entry if volatility requires wider invalidation level.
How is position size calculated?
The formula is: sharesToBuy = riskBudget / riskPerShare, where riskBudget = portfolioValue times (riskPct / 100) and riskPerShare = entryPrice stopLossPrice. For example, with a $100,000 portfolio risking 1%, your risk budget is $1,000. If you enter at $50 with a stop at $45, risk per share is $5, so you buy 200 shares. The total position cost is $10,000 but your maximum loss is only $1,000. One hundred thousand portfolio at one percent risk budgets one thousand dollars loss per trade maximum.
What risk percentage should I use per trade?
The common rule among professional traders is to risk no more than 1% to 2% of your portfolio per trade. At 1% risk, you would need 100 consecutive losing trades to lose your entire portfolio, which is extremely unlikely with a sound strategy. At 2% risk, it would take 50 consecutive losses. The key is consistency: always define your stop loss before entering and size accordingly so that a single bad trade never threatens your capital base. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position.
How do I choose a stop-loss price?
The stop loss price is the level at which you will exit the trade if it moves against you. It defines your maximum risk per share and is essential for position sizing. Without a stop loss, you cannot calculate position size because you do not know your risk per share. The stop should be placed at a level that invalidates your trade thesis, such as below a support level for a long position. Never move a stop loss further away to avoid being stopped out.
What does the position sizing calculator tell me?
The tool calculates four key outputs: the number of shares to buy, the total position cost (shares times entry price), the dollar amount at risk (shares times risk per share), and the position size as a percentage of your total portfolio. The position cost will typically be much larger than the risk amount, which is normal. What matters is the risk amount, which should never exceed your predetermined risk budget. Tighter stops allow larger share counts at identical risk budget, explaining day trader size versus swing trader size.
How do I use this position size calculator on phone or tablet?
Yes. Position Sizing Calculator runs entirely in your mobile browser with the same formulas as desktop. Optional localStorage may remember inputs on your device when enabled in browser settings.
Where is my data stored when I use Position Sizing Calculator?
Nowhere on our servers. Calculations execute locally in your browser. Optional localStorage saves form fields on your device only and never transmits portfolio numbers over the network.
Should I rely on Position Sizing Calculator for tax or legal decisions?
No. Position Sizing Calculator provides educational math only. Tax law, account rules, and personal circumstances vary. Consult a qualified tax or legal professional before transactions with material consequences.
Related Tools
Use with the Risk to Reward Ratio Evaluator to assess trade quality, or the Trailing Stop Loss Router for dynamic stop management. Entry fifty with stop forty five implies five dollar risk per share and two hundred share position. Position cost ten thousand can coexist with one thousand risk when stop defines loss cap not capital deployed.