Position sizing

The calculation

risk amount = equity × risk per trade
stop distance = |entry − stop loss|
value per unit = contract size × tick value (per instrument)

lot size = risk amount / (stop distance × value per unit)

The result is then clamped to the broker's minimum lot, step size and your own max lot size. If clamping would force the trade above your risk budget, the signal is rejected instead.

A worked example

Equity            10,000 USD
Risk per trade    0.5%          → 50 USD at risk
Signal            BUY EURUSD 1.0850, SL 1.0800
Stop distance     0.0050        → 50 pips
Pip value         10 USD per pip per standard lot

lot size = 50 / (50 × 10) = 0.10 lots

Why metals and indices trip people up

Contract size differs per instrument and per broker. Gold is often 100 ounces per lot, an index CFD might be 1 or 10 contracts per point, and micro variants divide everything by ten. Sizing from a forex assumption on a gold signal is how a 0.5% risk becomes 5%.

• PipSync reads the contract spec from your broker per symbol rather than assuming.
• Suffixed symbols (.m, micro) carry their own specs — re-check sizing after changing a symbol mapping.
• If a spec cannot be read, the trade is rejected instead of sized on a guess.

Margin and free equity

Sizing is about risk, but the broker also needs margin. A correctly-sized position can still be rejected for insufficient free margin when several trades are already open.

• Max open positions is the practical margin control — cap the book, not just each trade.
• Watch free margin during high-volatility sessions; floating loss eats it before any stop is hit.
• Rejections for margin appear in the trade log with the broker's own message.