Position sizing for beginners

The basic formula

Quantity = amount willing to risk ÷ (entry price − stop price), using the absolute price difference. If a synthetic practice account allows a 500-rupee risk, an entry is 250 and the stop is 245, the per-unit risk is 5. The calculation gives 100 units.

This simple example ignores brokerage, slippage, taxes, lot sizes and personal circumstances. Those details matter in real-world decisions, which is why this article does not recommend a real trade or account allocation.

Why entry and stop come first

You cannot size a position responsibly until you know where the idea fails. A wider stop means more risk per unit and therefore fewer units for the same chosen risk amount. Changing the stop after calculating the quantity changes the plan.

Synthetic practice example

Common mistakes

• •Choosing quantity before defining invalidation.
• •Ignoring the distance to the stop.
• •Treating a formula as financial advice.
• •Increasing quantity to recover a prior result.

Disclosure

TradeTrainer uses fictional instruments and synthetic OHLC candles for education. This is not financial advice, a recommendation, or a promise about trading outcomes.