How to calculate position size in MetaTrader 5

Most of us pick the lot first. It feels about right, so the stop ends up wherever the money feels comfortable. Do it the other way round and the lot is no longer a feeling. It's just arithmetic. Every trade then risks the same share of the account, whether the stop is 8 pips away or 80.

The formula

Lot size = money at risk / (stop distance × value of that distance for 1 lot)

• Money at risk is what you accept to lose if the stop is hit. A lot of traders use a percent of the balance. 1% of a 10,000 account is 100.
• Stop distance is entry price minus stop price, in price units.
• Value for 1 lot is what one lot gains or loses over that distance. It depends on the contract size. If the quote currency isn't your account currency, it also depends on the exchange rate.

The standard order window in MetaTrader 5 asks for volume in lots. It won't work the lot out from your stop. You either do the sum yourself or use a tool that does it for you.

Where to find the numbers in MetaTrader 5

1. Open Market Watch (Ctrl+M).
2. Right-click the symbol and choose Specification.
3. Look for three lines: Contract size, Minimal volume and Volume step.

Contract size tells you what 1 lot is. For most forex pairs that's 100,000 units of the base currency. For gold it's often 100 ounces. Minimal volume and volume step decide how your lot gets rounded.

Example 1: EURUSD, account in USD

• Risk: 100 (1% of 10,000).
• Entry 1.08500, stop 1.08300. That's 0.00200, or 20 pips.
• 1 lot is 100,000 euros. A move of 0.00200 is worth 200 per lot.
• Lot = 100 / 200 = 0.50.

Example 2: USDJPY, account in USD

Here gains and losses come out in yen. So there's one extra step to get them into your account currency.

• Risk: 100.
• Entry 150.000, stop 149.700. That's 0.300, or 30 pips.
• 1 lot is 100,000 dollars. 0.300 is worth 30,000 yen per lot.
• At 150 yen to the dollar, 30,000 yen is 200 per lot.
• Lot = 100 / 200 = 0.50.

The conversion uses today's rate. The same 30-pip stop is worth a bit more or a bit less tomorrow, so don't reuse yesterday's lot.

Example 3: gold (XAUUSD), account in USD

• Risk: 100.
• Entry 4455.13, stop 4450.12. That's 5.01.
• With a contract size of 100 ounces, 5.01 is worth 501 per lot. Not every account uses 100 ounces. Check yours in the Specification window.
• 100 / 501 = 0.1996. With a volume step of 0.01 you get 0.19.

What the formula leaves out

Lot steps and the minimum lot. Lots go in steps, usually 0.01, with a minimum size. Rounding down keeps you at or under your risk. Sometimes even the minimum lot is too big for your stop. Then the trade risks more than you planned. Better to find that out before you send it.

Commission. Say your account charges 7 per lot round turn. Add it to the cost of one lot. In the EURUSD example that's 207 per lot instead of 200. 100 / 207 = 0.48.

Swap and slippage. Swap is charged when you hold overnight. Slippage happens when the market moves fast. You can't know either one when you open the trade, so no calculation covers them in advance. Your number is the risk to the stop. It isn't a cap on the loss.

Percent or fixed amount?

With a percent, the lot gets smaller after losses and bigger after wins. A bad run hurts less. A fixed amount is easier to read: every trade is the same size in money. Either one works. What matters is that you pick the number before the trade, not in the middle of it.

Common questions

Tomky, Dojiwave · Updated 14 November 2026