The standard sizes
| Type | Units | Notation | Pip value (dollar pair) |
|---|---|---|---|
| Standard | 100,000 | 1.00 | $10 |
| Mini | 10,000 | 0.10 | $1 |
| Micro | 1,000 | 0.01 | $0.10 |
The micro lot is the minimum at most brokers, which matters for small accounts: if your calculated risk implies less than 0.01 lots, the account mathematically cannot take that trade.
Size is an output, not a choice
The common error is choosing size first and then looking for somewhere to put the stop. The correct order is reversed: set the stop from the chart, then derive size from your risk percentage and the stop distance. That keeps what you risk constant however the trade changes. See the steps of a trade.
The formula
Position size = (capital × risk %) ÷ (stop distance in pips × pip value)
A worked example
A $2,000 account, 1% risk ($20), and a 40-pip stop on a pair worth $10 per pip per full lot. Size = 20 ÷ (40 × 10) = 0.05 lots. Widen the stop to 80 pips and size becomes 0.025 lots — while the maximum loss stays $20 in both cases.
Common mistakes with this term
- Fixing size across trades despite different stop distances, so real risk varies unnoticed.
- Choosing size from available margin instead of a defined risk percentage.