Start with the risk-based share count
For a long trade, decide how much of the account you are willing to put at risk and where you plan to exit if the trade is wrong. The basic estimate is:
If you risk $250 with an $84.50 entry and an $81.25 stop, the estimate is 250 ÷ 3.25 = 76.92 shares. Without fractional shares, round down to 76. Rounding to the nearest share could put you above the budget you selected.
For a short trade, reverse the price difference: Stop − Entry. A stop on the wrong side of the entry is an invalid setup, not a negative share count.
Then check what you can actually fund
Risk-based sizing does not know how much cash you have. If your broker allows no leverage, your position still has to fit the available buying power.
With $2,000 cash, that same $84.50 stock permits at most about 23 shares before costs—not 76. You can accept the smaller planned dollar risk or choose a different trade; you cannot solve the mismatch by ignoring it.
RiskSized includes entry fixed and percentage commissions in this cap. If leverage is enabled, it multiplies the buying-power assumption, but your broker's actual margin requirement may be higher.
Add a maximum account allocation
Even a funded position may be too concentrated for your plan. A 20% allocation cap on a $10,000 account means $2,000 of notional exposure, regardless of what the stop distance suggests.
Use the smallest of all three
A complete long example
| Input | Value |
|---|---|
| Account equity / risk | $25,000 / 1% = $250 |
| Entry / stop | $84.50 / $81.25 |
| Available cash | $12,000, no leverage |
| Maximum allocation | 35% = $8,750 |
Before costs, the limits are approximately 76.92 risk shares, 141.98 cash shares, and 103.55 allocation shares. The risk limit is smallest, so the whole-share plan is 76.
Increase the entry price or tighten the stop and another constraint may become binding. The important output is not just the number—it is knowing which guardrail produced it.
If you assume $0.02 of adverse slippage on both entry and stop, the long's estimated per-share risk becomes ($84.50 + $0.02) − ($81.25 − $0.02) = $3.29. RiskSized uses this adjusted risk before calculating size.
What the result does not mean
The estimated stop loss is not a guaranteed maximum loss. A gap or poor liquidity can produce a worse fill. Nor does a position that fits cash mean it is suitable for you. Diversification, volatility, taxes, margin rules and the possibility of losing the entire investment remain outside this simple calculation.
Use the planner to make these assumptions visible, then check the actual order and margin details with your broker.