Position sizing in Scalper determines how order quantity is calculated when placing trades from Charts. It allows exposure to be controlled based on capital, lot size, or available margin before executing a trade.
Position sizing options in Scalper
Scalper supports three position sizing methods:
Only one method can be active at a time.
Amount-based position sizing (Amt)
When amount (Amt) is selected:
- You enter the total amount you want to deploy in the trade
- Quantity is calculated based on the net premium of the order
- Quantity may change if the price changes before order placement
- Auto-update quantity can be used to recalculate quantity when the price moves
This method is used when you want to cap exposure by value.
Lot-based position sizing (Lots)
When a lot is selected:
- You enter the number of lots you want to trade
- Quantity is calculated strictly based on the instrument’s lot size
- Quantity does not change with price movement
- Auto-update quantity has no impact in this mode
This method is useful when trading derivatives where a fixed lot size is required.
Margin-based position sizing (% Margin)
When % Margin is selected:
- You enter the percentage of available margin to be used for the trade
- Quantity is calculated based on available margin and current price
- Quantity may change if available margin or price changes
- Auto-update quantity helps adjust quantity before order placement
This method is useful when you want to control risk relative to your total margin.
Auto-update quantity behaviour
When it is enabled:
- Quantity is recalculated automatically before order placement
- This is most relevant for amount and % margin–based sizing
- If disabled, the calculated quantity remains fixed.
Amount and % margin–based sizing benefits from auto-update quantity, while lot-based sizing always remains fixed.
What if...
| Scenario | Solution/Outcome |
|---|
| Amount or % margin is selected, and the price changes | Qty recalculates automatically if auto-update is enabled. |
| Available margin changes before placing the order | Qty may change, or the order may be rejected. |
| Lot-based is selected | Qty remains fixed regardless of price movement. |
| Calculated qty is below the minimum tradable qty | The order cannot be placed, and qty must be adjusted. |
| Auto-update qty is disabled | Qty remains unchanged even if price changes. |
Last updated: 12 Feb 2026