Position Size Calculator [Free Tool]
Size every trade from the money you are willing to lose, not from how confident you feel. Works for forex lots, stock shares, and crypto coins — with costs included.
Disclaimer: Trading financial instruments involves risk, and everything on this page is provided for educational purposes only. Nothing here is financial advice or a recommendation to buy or sell any instrument.
Position Size (lots)
0.19
Risk Amount
$200.00
Stop Distance
100.0 pips
Position Value
$20900.00
Position sized so your maximum loss if stopped out stays at or below your risk budget.
How is this calculated?
Lot Size = Risk Amount ÷ (Stop Distance × Pip Value)
Risk Amount = Balance × Risk%
Trading cost is deducted from the risk budget before sizing.
Read the full user guide
Every parameter, formula, and worked example — a complete reference for this tool.
What is position sizing, and why does it matter?
Position sizing decides how much you buy or sell on a single trade. The idea is simple but powerful: you start from the amount of money you are willing to lose, then work backwards to the number of shares, lots, or coins that keeps your loss inside that budget if your stop is hit. Get this right, and no single trade can seriously damage your account. The position size calculator below does the arithmetic for you across forex, US stocks, and crypto.
Key concepts
Risk amount
The maximum dollar loss you accept on one trade, usually set as a percentage of your account balance (commonly 1% to 2%) or as a fixed amount.
Risk distance
The gap between your entry price and your stop. The wider the stop, the smaller the position you can hold under the same risk budget.
Pip value
In forex, the profit or loss per pip reflects the contract size, pip size, and the quote-to-account exchange rate.
A worked example with real numbers
- 1
Set the risk budget
You have a $10,000 account and decide to risk 2% per trade, so your risk amount is $200. That is the number the position cannot afford to lose.
- 2
Measure the stop distance
You plan to buy a stock at $100 with a stop at $96. The risk distance is $4 per share.
- 3
Divide to get the size
Position = $200 ÷ $4 = 50 shares. If the stop is hit, 50 shares × $4 = $200, exactly your budget before costs.
- 4
Subtract costs first
If commission and slippage total $12, your usable risk is $188, so the correct size is 47 shares — $188 ÷ $4, rounded down.
How to use it
Choose the asset type
Forex (lots), US stocks (shares), or crypto (coins). The calculator adapts its units and formulas automatically.
Enter your balance and risk percentage
For example, a $10,000 account risking 2% allows a maximum loss of $200 per trade.
Enter the entry and stop prices
The difference between them is your risk distance, which drives the position size directly.
Deduct trading costs and read the result
The calculator subtracts commission and slippage from your risk budget before sizing the position, so the real loss stays inside budget.
The formula, step by step
Forex
Lots = (Balance × Risk% − Costs) ÷ (Stop distance in pips × Pip value)
Rounded down to the nearest 0.01 lot for a conservative position.
US stocks / crypto
Shares or coins = (Balance × Risk% − Costs) ÷ (Entry − Stop)
US stocks use whole shares only and round down.
Mistakes traders make
✗ Sizing a position from how confident you feel, not from the risk math
✓Confidence should change whether you trade, not how much you risk. The size must come from the stop distance and the risk budget, every time.
✗ Risking the same dollar amount on every trade regardless of volatility
✓A $200 risk on a quiet stock and on a wild crypto coin are completely different bets. Volatility-adjusted sizing keeps the danger level consistent.
✗ Ignoring costs so the 'safe' size quietly overshoots the budget
✓Commissions and slippage are real money. Subtract them before dividing, or your loss will exceed the risk you planned.
✗ Doubling the size after a loss to 'win it back'
✓That is revenge sizing, and it accelerates the drawdown. Stay with the same percentage every trade so one bad day cannot become a ruinous one.
When this tool fits — and when it does not
Use it when
- ✓Before every trade you place, as the final check that the loss stays inside your risk budget.
- ✓When your stop distance changes (a new setup means recalculating the size).
- ✓When comparing a volatile instrument against a calm one, to keep dollar risk constant.
Skip it when
- ✗Sizing a position without a defined stop loss — there is no denominator to divide by.
- ✗As a replacement for a full trade plan; size is one leg of the decision, not the whole thing.
- ✗When you are chasing a large position for its own sake rather than sizing to risk.
Practical tips that actually help
Keep the percentage fixed, not the dollar amount
As your account grows, the same 1-2% buys bigger positions naturally. As it shrinks, sizes shrink too — a self-correcting feedback loop.
Widen the stop, shrink the size — never both at once
If a setup genuinely needs a wide stop, accept the smaller size it implies. Widening the stop while keeping the same size doubles your risk without you noticing.
Recompute after costs, every time
Slippage varies with the market. Check the current spread before you divide, especially on less liquid names and fast-moving crypto.
Related & next steps
Stop Loss & Take Profit
Turn a risk amount into exact stop and target price levels.
Risk to Reward Ratio
Judge whether the trade's payoff is worth the risk.
Risk of Ruin
See how a string of losses could erode your account.
Backtest your sizing rule
See how a fixed-percentage sizing rule survives long losing streaks on historical data.
Frequently asked questions
How much should I risk per trade?▾
A common starting point is to risk no more than 1% to 2% of your account on any single trade. That is not a profit target — it is a conservative guardrail that keeps a losing streak from shrinking your account too quickly. Adjust it only after you understand your own tolerance for drawdown.
Why does a wider stop mean a smaller position?▾
Position size equals your risk amount divided by your stop distance. A wider stop means each unit of price movement costs you more, so the same risk budget only buys a smaller position.
Why subtract trading costs from the risk budget?▾
Commissions, spreads, and slippage are real losses. If you ignore them, your actual loss when the stop triggers will exceed the budget and your risk control quietly stops being accurate.
What happens if my stop distance is zero?▾
A zero or missing stop distance cannot produce a position size, because dividing by zero is undefined. Always enter a stop price below your entry for a long trade (or above it for a short trade) before calculating.
Is a bigger position always better?▾
No. A bigger position raises both potential profit and potential loss. Sizing should follow your risk budget and stop placement first — chasing a larger position just to 'make more' is how small accounts get hurt quickly.
Does position sizing work the same in crypto?▾
The principle is identical, but the inputs differ. Crypto is priced in coins rather than shares or lots, and volatility is often higher, so wider stops and smaller sizes relative to your account are common.
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The formulas on this page are based on widely used risk-management methods for spot forex, US stocks, and cryptocurrency. Contract specifications and fees vary by broker, so always check the actual conditions of your own account.
Disclaimer: The tools and content on this site are provided for educational purposes only and do not constitute investment advice. Trading and investing involve a substantial risk of loss, and past performance does not guarantee future results.