Position Size Calculator – Risk-Based Trading Sizer

Position Size Calculator

100% free · Runs 100% in your browser · No signup needed

Position size (units) = risk amount ÷ |entry − stop|. If the stop is below the entry it is a long trade; above the entry it is a short trade. Risk:reward = |target − entry| ÷ |entry − stop|, shown only when a target is entered.

Try an example: $10,000 @1% risk, entry 0.02, stop 0.019

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What Is Position Sizing?

Position sizing is the risk-management discipline of deciding how much to trade — not whether the trade is good, but how big it should be so that a loss stays within your plan. Professional traders think in risk first: they decide the maximum they are willing to lose on one idea, then work backward to the number of shares, contracts, or coins that keeps the loss at that level. Our free Position Size Calculator automates that math: enter your account size, your risk percentage, your entry price, and your stop-loss, and it returns the position size in units, the notional value, and the risk-to-reward ratio when you add a profit target.

The Position Sizing Formulas

The calculator uses the standard risk-management math:

• Risk amount = account size × risk percent. This is the most you plan to lose if the stop-loss is hit.
• Position size (units) = risk amount ÷ |entry − stop-loss|. The distance between entry and stop defines how many units that risk amount buys.
• Notional value = units × entry price. The total market value of the position.

Worked Example: 100,000 Units, $2,000 Notional

Here is the verified example built into this tool. Take a $10,000 account with a 1% risk per trade: risk amount = 10,000 × 0.01 = $100. With an entry at 0.02000 and a stop-loss at 0.01900, the distance is |0.02000 − 0.01900| = 0.001, so position size = 100 ÷ 0.001 = 100,000 units. The notional value is 100,000 × 0.02 = $2,000. If the stop is hit, the loss is about $100 — exactly the planned 1% — even though the position controls $2,000 of market exposure. That separation between exposure and risk is the whole point of position sizing.

How to Use This Position Size Calculator

1. Enter your account size — the total trading capital you are working with.
2. Set your risk percent — use the slider (0.25% to 5%). Most educators suggest 1% or less per trade; this is a planning input, not a safety guarantee.
3. Enter the entry price — where you plan to open the position.
4. Enter the stop-loss price — where you will exit if the trade goes wrong. Never size a position without one.
5. Optionally add a profit target — the tool then shows the risk-to-reward ratio (for example, risking $100 to make $300 is 1:3).
6. Read your outputs — risk amount in currency, position size in units, notional value, and risk-to-reward, all updated live.

Why the 1% Rule Exists

Risking a small, fixed fraction per trade means a losing streak cannot wipe you out. Ten consecutive losses at 1% risk each leave you with about 90% of your account; the same streak at 10% risk each leaves about 35%. The math of recovery is brutal — a 50% drawdown needs a 100% gain just to break even — so keeping individual risk small is how traders stay in the game long enough for an edge to play out. The calculator's 0.25%–5% slider covers everything from ultra-conservative to aggressive, but the discipline matters more than the exact number.

Practical Examples

• Forex: the worked example above — $10,000 account, 1% risk, entry 0.02000, stop 0.01900 → 100,000 units with $2,000 notional and $100 planned risk.
• Crypto: a $25,000 account at 2% risk gives a $500 risk amount. Entry $67,000, stop $64,000 → 500 ÷ 3,000 = 0.1667 BTC, notional ≈ $11,167.
• Stocks: a $50,000 account at 1% risk gives $500. Entry $150, stop $140 → 500 ÷ 10 = 50 shares, notional $7,500. With a $170 target, the risk-to-reward is 1:2.
• Tight vs. wide stops: halving the entry-to-stop distance doubles the position size for the same risk — the calculator makes that trade-off visible before you commit.

Risk-to-Reward, Explained

When you add a profit target, the tool divides the potential reward by the planned risk. A 1:2 ratio means you stand to gain twice what you risk; a 1:3 ratio, three times. Many traders filter for setups offering at least 1:2, because with that ratio a strategy can be right less than half the time and still grow. The calculator shows this instantly so you can judge whether the trade is worth the risk before placing it.

Educational Tool Only — Not Financial Advice

This calculator is an educational tool only and not financial advice. Real fills differ from textbook math: brokerage fees, spread, slippage, and price gaps that blow past your stop are not modeled here, so actual losses can exceed the planned risk amount. A risk percentage is a planning input, not a safety guarantee — markets can and do move discontinuously. Always do your own research, understand the products you trade, and never risk money you cannot afford to lose. If you are unsure, speak to a licensed financial professional.

Frequently Asked Questions

Why is position size based on the stop distance? Because the stop defines your loss per unit. A wider stop means each unit risks more, so you need fewer units to keep total risk constant — the formula keeps the math honest.

What risk percentage should beginners use? Educational resources commonly suggest starting at 1% or less per trade while learning. This tool accepts 0.25%–5% so you can model different approaches.

Does this work for leveraged products? The unit math is the same, but leverage magnifies both gains and liquidation risk beyond what this simple model shows — treat leveraged sizing with extra caution.

What if my stop gets gapped through? Then your loss can exceed the calculated risk amount. That is one of the real-world effects this educational model does not include.

Is my data private? Yes — every number you enter is processed in your browser and never sent anywhere.

Position Sizing and Leverage

The unit math in this calculator works the same whether you trade spot or leveraged products — but leverage changes what the numbers mean for survival. A 100,000-unit forex position with $100 of planned risk behaves very differently at 2:1 leverage versus 50:1 leverage: higher leverage means a smaller adverse move triggers a margin call, potentially closing you out before price ever reaches your stop. The calculator shows notional value precisely so you can see your true market exposure, not just the risk amount. As a rule of thumb taught in most risk-management courses, beginners should master unleveraged or low-leverage sizing first; leverage multiplies the speed of outcomes, including the bad ones, and none of that acceleration appears in a simple position-size formula.

Common Position Sizing Mistakes

• Sizing without a stop: the entire formula hinges on the entry-to-stop distance. No stop means no defined risk, which means no valid position size — only a gamble.
• Moving the stop further when wrong: widening the stop after entering breaks the risk plan the size was built on. The disciplined move is to accept the planned loss.
• Risking the same percent on correlated trades: three positions in highly correlated assets at 1% each is closer to 3% risk on one idea. Consider correlation when stacking positions.
• Ignoring costs: spread and commission widen your effective stop distance on every trade. For scalpers with tight stops, costs can dwarf the planned risk.
• Martingale sizing: doubling size after losses to "win it back" is the fastest known route to a blown account. Fixed-fractional sizing exists to prevent exactly this.

Paper-trade the math first: before risking real capital, run twenty hypothetical trades through this calculator with your planned risk percent and typical stop distances. You will internalize how stop distance controls size, how risk-to-reward shapes outcomes, and — most importantly — whether you can emotionally tolerate the losing streaks that even good strategies produce. Education first, capital second: that ordering is what separates traders who last from those who donate.

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