What is the Position Size Calculator?
A position size calculator tells you exactly how many shares, contracts, or units to trade so that — if your stop-loss is hit — you lose only a fixed, pre-decided percentage of your account. Position sizing is widely considered the single most important habit separating consistent traders from accounts that blow up.
Instead of guessing how big a trade should be, you anchor every position to your risk tolerance and the distance to your stop. The result is steadier equity curves and the freedom to be wrong many times in a row without serious damage.
How to use it
- 01Enter your total account balance — the capital you actually trade with.
- 02Choose the percentage you are willing to risk on this trade. Most professionals risk 1–2% per position.
- 03Enter your planned entry price and your stop-loss price. The gap between them is your risk per share.
- 04Optionally add a take-profit price and per-side commission to see your risk/reward and net numbers.
- 05Read the recommended position size — the maximum shares you can hold while keeping your loss within budget.
The formula
The numerator is the most money you allow yourself to lose; the denominator is how much you lose per share if the stop is hit.
Worked example
Suppose you have a $10,000 account and risk 2% per trade, so your maximum loss is $200.
You plan to buy at $150 with a stop-loss at $145, making your risk $5 per share.
Position size = $200 ÷ $5 = 40 shares. Buying 40 shares means a stop-out costs exactly $200 — your planned 2%.
Frequently asked questions
How much of my account should I risk per trade?+
Most experienced traders risk 1–2% of their account on any single trade. Risking more than 3–5% means a normal losing streak can quickly cause severe drawdowns that are mathematically hard to recover from.
What is position sizing in trading?+
Position sizing is the process of deciding how large a trade should be based on your account size, your risk tolerance, and the distance to your stop-loss — rather than a fixed dollar amount or a gut feeling.
Does this calculator work for forex and crypto?+
Yes. The same formula applies to any market — enter the price levels in the instrument's units. For forex, size in units or lots; for crypto, use the coin price and your stop distance.
Why is position sizing more important than picking winners?+
Even a strategy with a high win rate will eventually hit a losing streak. Correct position sizing guarantees that no single trade — or run of trades — can do irreversible damage, which is what keeps you in the game long enough to profit.
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For educational purposes only. Not financial advice.