Position sizing 101

Two traders can take the exact same trade — same entry, same stop, same target — and one loses 1% of their account while the other loses 25%. The difference is position size. It's the single most important number you choose on every trade, and it's the one beginners think about least. By the end of this lesson you'll be able to size any position correctly in under a minute.

What you'll learn

• Why position size, not entry, decides how much you lose when you're wrong
• The position-sizing formula, step by step
• Worked examples for EUR/USD, USD/JPY, and gold
• Why you always round down
• The correct order of decisions: stop first, size second

1. The order of decisions

Most beginners decide in this order: "I'll trade 1 lot... where should my stop go?" Professionals decide in the opposite order:

1. Where is my trade idea proven wrong? → that's the stop-loss.
2. How much am I willing to lose if it is wrong? → that's the risk amount.
3. What position size makes those two numbers match? → that's the position size.

The stop comes from the chart. The risk comes from your rules. The size is simply the result of the calculation.

2. The formula

Position size (lots) = risk amount ÷ (stop distance × value per pip per lot)

Where:

• Risk amount = account balance × risk percentage (e.g. $5,000 × 1% = $50)
• Stop distance = pips (or dollars) between your entry and your stop-loss
• Value per pip per lot = $10 for a standard lot of pairs quoted in USD (EUR/USD, GBP/USD, AUD/USD)

3. Worked example: EUR/USD

(Illustrative.)

• Account: $5,000
• Risk per trade: 1% → risk amount = $50
• Entry: 1.0850, stop-loss: 1.0825 → stop distance = 25 pips
• Pip value: $10 per standard lot

Position size = $50 ÷ (25 × $10) = $50 ÷ $250 = 0.20 lots

Check: 0.20 lots = $2 per pip. 25 pips × $2 = $50. ✓

Now watch what happens if the stop needs to be wider:

The risk stays at $50 every time. A wider stop just means a smaller position. This is how professionals keep losses consistent no matter how the setup looks.

4. Worked example: gold (XAU/USD)

Gold is usually measured in dollars, not pips. At many brokers, 1 lot = 100 oz, so a $1 move = $100 per lot. (Contract sizes vary — check your broker.)

(Illustrative.)

• Account: $5,000, risk 1% → $50
• Entry: $2,350.00, stop: $2,342.00 → stop distance = $8.00
• Value of a $1 move per lot: $100

Position size = $50 ÷ ($8 × $100) = $50 ÷ $800 = 0.0625 lots → round down to 0.06 lots

Check: 0.06 lots × $100 × $8 = $48 — just under the $50 limit. ✓

5. Worked example: USD/JPY

When the US dollar is the first currency in the pair, the pip value isn't a fixed $10 — it depends on the exchange rate.

For USD/JPY, 1 pip = 0.01, and 1 standard lot = 100,000 USD, so:

• Pip value per lot = 100,000 × 0.01 = ¥1,000
• In dollars, at USD/JPY = 150.00: ¥1,000 ÷ 150 = $6.67 per pip

(Illustrative.) Account $5,000, risk 1% ($50), stop 30 pips:

Position size = $50 ÷ (30 × $6.67) = $50 ÷ $200.10 = 0.2499 → round down to 0.24 lots

6. Always round down

Lot sizes come in fixed steps (usually 0.01 lots). When your calculation doesn't land exactly on a step, round down. Rounding up means risking more than your rule allows — and small rule-breaks become habits.

7. Lot sizes at a glance

If your correct size comes out below 0.01 lots, the trade's stop is too wide for your account at that risk level. Skip it, or find a setup with a tighter logical stop.

Common beginner mistakes

• Using the same lot size on every trade, so losses swing wildly with stop distance.
• Choosing the size first and then squeezing the stop to fit — putting it inside normal market noise.
• Widening the stop mid-trade without reducing size — multiplying the planned risk.
• Assuming every instrument is $10 per pip. Gold, JPY pairs, indices, and crypto all differ.
• Rounding up "just this once".

Key terms

Practice

1. Using your real (or planned) account size and 1% risk, calculate the position size for:
   • EUR/USD with a 20-pip stop
   • EUR/USD with a 60-pip stop
   • XAU/USD with a $12 stop (check your broker's contract size)
2. Place each as a demo trade with the stop attached, then check the platform's projected loss at the stop. Does it match your calculation?
3. Write the formula on a card and keep it by your screen until you no longer need it.

Quick recap

• Decide in this order: stop → risk amount → position size.
• Position size = risk amount ÷ (stop distance × value per pip per lot).
• A wider stop means a smaller position; the money at risk stays the same.
• Pip values differ across instruments — know yours before you trade.
• Always round down, and never move a stop to fit a size.