Risk management
What is position size?
Understand position size, risk amount, Stop Loss distance and why the same lot size does not create the same risk on every instrument.
You are about to trade XAUUSD. Your account balance is 1,000 USD and you have chosen a Stop Loss, but you are unsure what lot size to enter. Position size is the volume that fits the loss you are willing to accept, not a number to pick from habit.
Four inputs to check
- The balance or equity used for the plan.
- The maximum risk you accept for this trade, as money or a percentage.
- The distance from entry to the Stop Loss.
- The contract specification for the exact symbol: tick size, tick value, minimum volume and volume step.
For example, if you choose a 1% risk limit on 1,000 USD, the trade’s risk budget is 10 USD. This illustrates the arithmetic only; it is not a recommended risk level for everyone.
From risk budget to volume
The general calculation is:
Position size = risk budget ÷ the projected loss at the chosen Stop Loss for 1 lot.
Suppose the symbol specification shows that the selected Stop Loss would result in a 50 USD loss with 1 lot. With a 10 USD risk budget, the calculation gives 0.2 lot. This is hypothetical: tick value, account currency and contract size can differ by symbol and broker.
On MT5, open the symbol specification and check tick size, tick value and volume step. If the result falls between valid volume steps, round down to the next valid step. If it is below the minimum volume, do not automatically raise it if that would exceed your risk budget.
Why can the same 0.10 lot mean different risk?
If two trades use the same symbol but one Stop Loss is 2 USD from entry and the other is 5 USD away, the second trade will usually have a larger projected loss, all else being equal. Move to NAS100 or another broker and the contract specification may change too.
Volume tells you the size of the position. To understand the risk, you also need the Stop Loss and the symbol’s contract details.
A pre-trade check
Set the entry from your plan, place the Stop Loss according to the trade logic, choose the risk budget, check the contract specification and then calculate volume. Slippage or fast market conditions can make the realized loss differ from the estimate.
For the effect of trading fees, read Spread, commission and swap. If you are still choosing where to trade, Compare Brokers can help narrow the options; calculate the final volume using the exact account and symbol.
