Position size calculator
An estimate for planning, not trading advice.
Free market tools, live on StockMarketCap
Estimate for planning only, not trading advice. Share count is rounded down so a stop-out stays within your risk budget; it ignores commissions, slippage, and gaps past your stop, any of which can make the real loss larger. Prices and risk percent are your own inputs.
Frequently asked questions
How is position size calculated from risk?
First the tool finds your risk budget in dollars: account size times the percent you are willing to risk per trade. Then it divides that by the per-share risk, which is the distance from your entry price to your stop-loss. The result is the number of shares whose loss at the stop equals your risk budget, rounded down so you never risk more than intended.
What is a good percent to risk per trade?
Many risk-management approaches keep the loss on any single trade to a small share of the account, often around one to two percent, so a string of losers does not do lasting damage. The right number is personal and depends on your strategy and tolerance.
What does the reward-to-risk (R multiple) mean?
R compares your potential reward to your risk. If your target is three times as far from entry as your stop is, the trade is 3R: you stand to make three dollars for every one at risk if both levels are hit. It is a way to judge whether a setup is worth taking before the trade, not a probability that the target is reached.
Does this account for fees, slippage, or gaps?
No. The share count keeps a clean stop-out within your risk budget, but it ignores commissions, slippage, and price gaps that jump past your stop, any of which can make the real loss larger than planned. Treat the output as a starting point for sizing, not a guarantee of your maximum loss.