Position Size Calculator: Calculate Exactly How Many Shares to Buy
Enter your account size, risk percentage, entry price, and stop loss — and get the exact number of shares to trade. Accounts for cash, margin, and day trading buying power so the number you get is one you can actually execute with your broker.
Dollar Risk = Account Size × (Risk % ÷ 100)
Risk Per Share = | Entry Price − Stop Loss |
Shares = ⌊ Dollar Risk ÷ Risk Per Share ⌋
Position Value = Shares × Entry Price
Shares are rounded down to whole numbers so your actual risk never exceeds your risk budget. If the position value exceeds your buying power, shares are further capped to what your account can afford.Next Step: Once you know your shares, check the setup with our Reward/Risk Calculator.
How to Use This Calculator
Select Your Trade Direction
Choose Long if you're buying (expecting price to go up) or Short if you're selling first (expecting price to go down). This matters because it changes how the calculator validates your stop loss — for longs, your stop must be below entry; for shorts, above.
Choose Your Account Type
Select Cash (1×) if you have a cash account with no margin. Choose Margin (2×) for a standard margin account. Choose Day Trade (4×) if you're a Pattern Day Trader with an account above $25,000 — this gives you 4:1 intraday buying power. The calculator uses this to make sure it never recommends more shares than your account can actually afford.
Enter Your Account Size
This is your total account balance — the number you see when you log into your broker. Not your net worth, not your "trading fund" — the actual cash and equity in the account you're trading from.
Set Your Risk Percentage
This is the maximum percentage of your account you're willing to lose if this trade hits your stop loss. Professional day traders typically risk 0.5–2% per trade. If you're a beginner, start at 1% or lower. The preset buttons — Conservative (1%), Moderate (2%), Aggressive (3%) — make this easy.
Enter Your Entry Price and Stop Loss
Your entry price is where you plan to buy (or short) the stock. Your stop loss is the price where you'll exit to limit your loss. The stop loss should be based on a technical level — a support zone, a moving average, or a chart structure — not an arbitrary dollar amount.
Read Your Results
The calculator instantly shows: the number of shares to trade, your actual dollar risk, risk per share, total position value, and buying power used. If your buying power limits the trade, the calculator tells you exactly how many shares were capped and why.
Example Scenarios
Example 1: Standard AAPL Long Trade
You have a $25,000 day trading account (4× buying power) and want to risk 2% per trade. You plan to buy AAPL at $185.00 with a stop loss at $182.50.
Buy 200 shares. If stopped out, you lose exactly $500 — 2% of your account.
Example 2: Small Account, Tight Budget
You have a $5,000 cash account (1× buying power) and want to risk 1%. You're looking at a $50 stock with a stop at $48.
Buy 25 shares. Clean, well-controlled trade on a small account.
Example 3: Buying Power Caps Your Position
Same $5,000 cash account, 1% risk, but this time you're looking at a $200 stock with a $0.50 stop (tight scalp).
The calculator caps you at 25 shares and explains why — protecting you from an order your broker would reject.
❓ Frequently Asked Questions (FAQ)
What is a position size calculator?
A position size calculator instantly tells you how many units, shares, or lots you should trade based on your account balance, risk percentage, and stop-loss distance. Instead of guessing, it calculates the exact trade size that keeps your risk under control.
Why is position sizing important in trading?
Position sizing controls how much of your account you risk on a trade. By calculating the right size, you avoid losing too much in one trade, survive losing streaks, and stay consistent over time. It’s one of the most critical parts of money management.
How do you calculate position size in trading?
The formula is:
Position Size = (Account Balance × Risk %) ÷ Stop Loss (per unit).
Example: You have a $10,000 account, want to risk 2% ($200), and your stop loss is $1 per share. Position Size = 200 ÷ 1 = 200 shares.
What formula does the position size calculator use?
It uses a risk-based formula:
Position Size = (Account Balance × Risk %) ÷ (Stop Loss × Value per Unit).
This works for stocks, forex, and crypto, adjusting automatically depending on the instrument.
How do you calculate position size in forex?
For forex:
Position Size (lots) = (Account Balance × Risk %) ÷ (Stop Loss in pips × Pip Value).
Example: You have $10,000, risk 1% ($100), stop loss of 50 pips, pip value $10 → 100 ÷ (50 × 10) = 0.2 lots.
How do you calculate position size in stocks?
For stocks:
Position Size = Risk per Trade ÷ Stop Loss (per share).
Example: $20,000 account, 1% risk ($200), stop loss $2 → 200 ÷ 2 = 100 shares.
What is the best risk percentage per trade?
Most professional traders risk 1–2% per trade. This keeps losses manageable and allows you to survive multiple losing trades. Aggressive traders may risk up to 5%, but this increases the chance of losing the account quickly.
Can a position size calculator help with money management?
Yes. By automatically calculating the correct trade size, it enforces strict risk rules, removes guesswork, and helps you stick to your money management strategy. This protects your capital and supports consistent growth.
How accurate is a position size calculator?
The calculator is mathematically precise when you enter correct account size, risk %, and stop loss. Accuracy also depends on broker settings, minimum contract sizes, and trading instrument rules.
What is the difference between lot size and position size?
Lot size is the standardized trading unit (for example, 1 lot in forex = 100,000 units).
Position size is the total number of units or contracts you are trading, which can include fractional lots.
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