Position sizing connects a trade idea to a defined amount of risk. It cannot make a trade safe or guarantee a particular loss, but it can make assumptions easier to inspect before an order is placed.
1. Start with the amount you are prepared to lose
Choose a hypothetical account value and a risk amount for planning. The simple relationship is:
Planned risk amount = account value × chosen risk fraction
For illustration only, if an account value is $5,000 and a trader chooses 0.5% as a planning input, the planned risk amount is $25. This is an arithmetic example, not a recommendation that 0.5% is appropriate for any person or account.
2. Measure the distance between entry and stop
For a long position, compare the planned entry price with the stop below it; for a short position, compare entry with the stop above it. The price distance alone is not enough: you must know how much one unit, contract, lot, or coin would lose over that distance in the account's currency.
3. Use the general sizing relationship
Estimated position size = planned risk amount ÷ estimated loss per unit at the stop
Suppose the planned risk amount is $25 and the instrument would lose an estimated $0.50 per unit if the stop were filled. The simple estimate is 50 units ($25 ÷ $0.50), before costs and execution differences. This example is deliberately generic; actual lot, contract, pip, tick, and quantity calculations vary by instrument.
4. Why Forex sizing needs extra care
Forex position sizing can depend on the currency pair, pip value, contract size, lot convention, account currency, and conversion rate when the quote currency differs from the account currency. Confirm the broker's contract specifications and pip-value calculation. A nominal lot size does not represent the same cash risk for every pair or account currency.
5. Why Crypto sizing is not always the same
Spot holdings, linear perpetual contracts, inverse contracts, and leveraged products can have different P&L, margin, funding, and liquidation mechanics. Leverage changes the margin needed and can amplify losses; it does not reduce the underlying market risk of a given position. Check the exchange's product rules, fees, funding, maintenance margin, and liquidation methodology before trading.
6. Account for costs and execution uncertainty
Spread, commission, funding, slippage, gaps, liquidity, and partial fills can make the realized result differ from a calculation. A stop order is not a guarantee of execution at the stop price. If costs are material, include a reasonable estimate in the plan and verify the result independently.
7. Validate the estimate before placing an order
- Confirm the correct symbol and product type.
- Check account currency, contract size, tick or pip value, and quantity increments.
- Confirm the stop is placed at the intended price and direction.
- Include trading fees and, where relevant, funding costs.
- Verify margin and liquidation rules directly with the broker or exchange.
- Recalculate after any change to entry, stop, or account balance.
Use the TRADEX workflow carefully
The TRADEX Trade Planner and Trade Calculator can help organize inputs and review estimates. Tool outputs depend on the data and assumptions supplied; verify critical calculations against the relevant broker or exchange before acting. Read our risk management guide and methodology and limitations for more context.
Important: This material is general education, not personal financial advice or a recommendation to trade. Forex, leveraged products, and crypto assets can cause substantial losses.