Why position size matters
Two traders can take the same setup and have completely different outcomes because of size. One trader risks 1% and survives a loss. Another risks too much and loses discipline after one candle.
Position sizing turns the trade idea into a number: how much you can lose if the stop is hit. This makes the trade planned instead of emotional.
The basic formula
Start with account size and risk percent. If you have a 100,000 account and risk 1%, the money at risk is 1,000. Then divide that risk amount by the stop distance and contract value to estimate size.
Example: if your planned risk is 500 and the stop distance is 25 pips, your size must keep the loss near 500 if price reaches the stop. The exact lot value depends on the pair and broker contract specifications.
Prop firm traders need an extra filter
In a challenge, your size should respect daily drawdown and max loss, not only your personal risk rule. A 1% risk may be too high if you are near the daily loss limit.
Before entry, ask: if this stop is hit, do I still have enough room to trade tomorrow? If not, the size is too large even if the setup looks clean.
Journal the size decision
Save the reason for your size in the trade note. Over time, you can see whether oversized trades come from FOMO, revenge trading, news events, or late entries.
This is where a trading journal becomes more than a record. It becomes evidence of your risk behavior.