MT5 Position Sizer: Size Your Lots by Risk Percentage

MetaTrader 5 does not ship a built-in position sizer. The "New Order" dialog only asks you to type a volume in lots, and nothing in the terminal converts your risk into that number. The standard way to size a position — used by brokers and the trading community alike — is the risk-percentage method: decide how much of your account you may lose on this trade, turn that into a money amount, then convert it into lots using your stop-loss distance and the symbol's pip value. The math is simple enough to do by hand, and several third-party tools (Expert Advisors, market utilities, web calculators) automate the same calculation. Whichever route you use, the decision stays yours: you pick the risk percentage and the stop, the calculator only does the arithmetic.

Why MT5 Doesn't Ship a Position Sizer

"Position sizer" describes a calculation, not a terminal feature. When you open an order in MT5, the Volume field takes lots directly — rounded to your broker's volume step — and the symbol specification (open it from the Market Watch for any instrument) carries the contract size, the volume minimum, and the volume step that your order must respect (MQL5 documentation on permitted volumes). The order flow is covered in the official MetaTrader 5 help on executing trades.

The terminal intentionally leaves sizing to the trader: there is no built-in, risk-based position-size calculator, which is exactly why an entire ecosystem of third-party position sizers exists (a broker-side summary of risk calculators for MT5, and FP Markets' explanation of what a Position Sizer Expert is).

When this fits: you know exactly how many lots you want and just want to place the order quickly.

The trade-off: the terminal gives you no guardrail. If you type 1.00 lot when the correct size is 0.10, the order goes through as typed, and the pip value differs from pair to pair — so the risk math is entirely on you.

The Risk-Percentage Method: the Calculation

Risk-percentage sizing means betting a fixed slice of your account on any single trade. Two steps:

1. Money at risk = account equity × risk %
2. Lots = money at risk ÷ (stop-loss distance in pips × pip value per lot)

Worked example. A $10,000 account, 1% risk per trade, stop-loss 20 pips away. Money at risk = $10,000 × 1% = $100. For a USD-quoted pair such as EURUSD, one standard lot (100,000 units) is worth about $10 per pip, so 20 pips × $10 = $200 of exposure per lot. $100 ÷ $200 = 0.5 lots.

Pip value is the part you must check. It follows from the symbol's contract size and quote currency: an XAUUSD or a non-USD-quoted pair needs a conversion step, which is why brokers teach the check — see TIOMarkets' risk-percentage walkthrough and Eightcap's position-sizing guide.

When this fits: any account size, any pair, any session — you can do it offline with a calculator or spreadsheet.

The trade-off: it is arithmetic you repeat on every trade, rounded to the broker's volume step, and each symbol needs its contract size double-checked. A small input error (wrong pip value, wrong stop distance) quietly changes the risk you actually take.

The Ecosystem: Tools That Automate the Same Math

You don't have to do the arithmetic by hand. Objective options that exist today:

• EarnForex PositionSizer — a free, open-source Expert Advisor that calculates position size from your risk and account parameters and can place the trade from its panel (GitHub repository).
• MQL5 Market utilities — commercial and free calculators sold per symbol or bundled, such as Lot Size Calculator By Percentage Of Balance and Position Size Calculator PRO.
• Broker-provided sizers — some brokers ship their own Position Sizer Expert to clients and document it (FP Markets).
• Web and chart tools — broker-hosted risk calculators and chart-side scripts such as TradingView's Positionsize script.

When this fits: you trade regularly and want a click instead of arithmetic, or you want an independent second check on your manual number.

The trade-off: each tool needs installation, attachment to a chart, or a login; some are paid, and every tool has its own input conventions. More importantly, a sizer only converts numbers you feed it — it never decides your risk percentage or your stop-loss, and no tool is mandatory.

Which Sizing Route Fits Which Scenario?

Combining Approaches — They Don't Rule Each Other Out

Manual and tool-assisted sizing complement each other rather than compete. A practical setup: keep the two-line formula in a spreadsheet as your baseline, use an EA panel for routine trades, and let a web calculator act as a second opinion whenever a pair has an unfamiliar contract size. What stays constant across all of them is the risk percentage you choose — the tools only automate the arithmetic, and the terminal itself never computes it for you.

If the goal is simply to watch the market and your open positions without opening the terminal, Camovia Tray turns MT5 into a tray tool — hover the tray icon for live quotes and view each open position's current P&L at a glance, with all data read locally from your terminal and staying on your computer.