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Trading Calculators
Calculate the right number of shares to buy for this trade from your acceptable loss relative to your account and your stop-loss price.
Many traders use 1 to 2%.
Enter your values and press Calculate
Right-sized quantity to buy
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Amount invested
Share of account
Reward-to-risk ratio
Risk management
If you size your trade so that you lose only 1 to 2% of your account when the stop-loss price is hit, you can protect your account even through a losing streak.
Decide your total account value and the percentage loss you are willing to take on a single trade.
Set the stop-loss price first, for example at a chart support level, then enter your entry price.
Quantity is set by acceptable loss ÷ loss per share. If it exceeds the weight cap, it is reduced automatically.
The reward-to-risk ratio (R) is (target price − entry price) / (entry price − stop-loss price). With a ratio of 2 or higher, the expected value can still be positive even with a 40% win rate.
Loss per share gets larger, so the quantity you can buy for the same acceptable loss shrinks. Stop-loss distance and quantity are inversely proportional.
If the stop-loss price is entered higher than the entry price, it is treated as a short position and calculated the same way.
If the stop-loss distance is very narrow, the calculated quantity can become excessively large. To prepare for situations where a stop-loss cannot be filled, such as a gap down, it is safer to also set a maximum weight per stock.
Results are estimates based on your inputs and simplified assumptions, and are for reference only, not a basis for investment decisions.
Last updated: November 2, 2026
A -50% loss needs a +100% gain. See at a glance the gain required to break even for each loss rate.
Calculate your new average price after buying more, and how many shares you need to reach a target average price.
If you bought on margin, see in advance how far the price can fall before you hit a collateral shortfall and forced liquidation.