Stock Share Size Calculator
Enter account size, risk %, entry, and stop. Get whole shares, dollar risk, and position value for a US equity trade.
How This Tool Works
US cash equities trade in whole shares. This tool applies the same 1% rule as the crypto risk calculator, then floors to a whole share so you do not send a fractional ticket on a name that does not allow it.
Dollar risk = Account × Risk%
Shares = floor(Dollar risk ÷ |Entry − Stop|)
If the stop is wider than the risk budget, the answer is zero shares — skip, do not round up. Overnight gap risk can still exceed the stop. Education only.
Formula
Dollar risk = account x risk % / 100
Risk per share = |entry - stop|
Shares = floor(dollar risk / risk per share)
Actual risk = shares x risk per share
Position value = shares x entry
Stocks trade in whole shares here, so the calculator rounds down. That keeps the actual risk at or under your cap, and it shows the unused budget so you can see the rounding.
Where it breaks: the stop protects nothing overnight. A stock that closes at $147 can open at $140, and a stop order becomes a market order at whatever price is there. Size for the gap risk on names that report earnings or trade thin.
Worked example
| Example account | Risk % | Entry | Stop | Risk/share | Shares (rounded down) | Actual risk | Position value | Unused budget |
|---|---|---|---|---|---|---|---|---|
| $25,000 | 1% | $150.00 | $147.00 | $3.00 | 83 | $249.00 | $12,450.00 | $1.00 |
| $10,000 | 1% | $42.50 | $41.80 | $0.70 | 142 | $99.40 | $6,035.00 | $0.60 |
| $50,000 | 0.5% | $8.20 | $7.95 | $0.25 | 1,000 | $250.00 | $8,200.00 | $0.00 |
| $10,000 | 2% | $300.00 | $285.00 | $15.00 | 13 | $195.00 | $3,900.00 | $5.00 |
FAQ
How many shares should I buy for a given stop?
Divide the dollars you're willing to lose by the distance from entry to stop, then round down. $250 of risk with a $3 stop distance is 83 shares.
Why does it round down?
Rounding up would put you over your risk cap. Rounding down keeps the loss at your stop at or under the number you picked.
What if the result is zero shares?
Your stop is too wide for your risk budget. Tighten the stop if the chart supports it, take a bigger risk only if you mean to, or skip the trade.
Do I need round lots of 100?
Most retail brokers fill odd lots without trouble. The calculator flags odd lots so you know, but you don't need to round to 100.
Related calculators
Risk & Position Size Calculator · Stop-Loss / Take-Profit Calculator · Break-Even After Loss Calculator
Glossary: Stop-Loss Order
Sizing math for education, not financial advice.
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All trading courses · Size before you open · Stock scanner · Crypto scanner · Journal
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