Position Size Calculator
Find the right number of shares or forex units to trade based on your account balance, risk per trade, entry price, and stop-loss.
Frequently Asked Questions
How much should I risk per trade?
Many traders risk just 1–2% of their account balance on any single trade. That keeps a string of losses survivable and lets your edge play out over many trades.
How is position size calculated?
Divide your risk amount (balance × risk%) by the per-unit risk. For stocks that is the distance between entry and stop-loss; for forex it is the stop in pips times the pip value.
Does it work for stocks and forex?
Yes. Switch between Stocks mode (entry and stop-loss prices give shares) and Forex mode (stop distance in pips and pip value give units or lots).
Understanding the Position Size Calculator
The Position Size Calculator tells you exactly how big a trade to take so a single loss never blows up your account. Instead of guessing share counts or lot sizes, you decide what percentage of your balance you are willing to risk, then the tool sizes the trade around your stop-loss. It works for both stock traders (in shares) and forex traders (in units or lots) and is fully currency-aware, so results display in your chosen currency. Everything runs in your browser with no sign-up, and a copy, CSV, and print bar lets you save each trade plan. Sizing positions by risk is one of the simplest habits that keeps traders in the game long enough for their edge to pay off.
How it works
Pick a mode, enter your account balance, and choose how much to risk per trade as a percentage (1-2% is common). The calculator multiplies balance by that percentage to get your dollar risk amount. In Stocks mode, you add an entry price and a stop-loss price; the gap between them is your risk per share, and dividing the risk amount by that gap (rounded down) gives the number of shares, plus the total position value. In Forex mode, you enter the stop distance in pips and the pip value per unit; the risk amount divided by stop pips times pip value gives the units (or lots) to trade. The tool validates that entry and stop differ and that every input is positive.
Worked example
Suppose your account holds $10,000 and you risk 1% per trade, giving a risk amount of $100. You plan to buy a stock at an entry of $150 with a stop-loss at $145, so your risk per share is $5. Dividing $100 by $5 gives 20 shares, and 20 × $150 means you commit $3,000 of capital while still risking only $100 if the stop is hit. Tighten the stop to $148 and the $2 per-share risk lets you buy 50 shares for the same $100 of risk.
Tips & common mistakes
- Most traders cap risk at 1-2% of account balance per trade so a losing streak stays survivable.
- Set your stop-loss based on the chart or strategy first, then let position size follow it - never widen the stop to fit a bigger position.
- Remember the position value is capital committed, not money at risk; your true risk is the smaller risk-amount figure.
- Account for spreads, slippage, and commissions, which can make your real loss larger than the modeled stop.
- In forex, double-check the pip value for your specific pair and lot size, since it changes with the quote currency.
- Recalculate position size as your balance grows or shrinks so your risk percentage stays consistent over time.
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Reviewed by the TopOpenTools editorial team · Last updated June 2026. These tools provide general estimates for educational purposes only and are not financial, tax, insurance, investment, or medical advice. Verify important decisions with a qualified professional.