Automatic lot sizing in an EA: balance, equity and stop distance

Automatic lots means that code calculates the requested volume. To understand a setting, identify its formula and inputs rather than relying only on a label such as automatic or dynamic.

Distinguish common sizing models

A balance-step model assigns a lot amount per balance unit. An equity-based model can react to open profit and loss. A stop-based model estimates volume from a chosen cash amount and the loss implied by an entry-to-stop move. These models can produce very different sizes from the same account balance.

Work through one illustrative calculation

Suppose a hypothetical balance-step rule assigns 0.01 lots for each 500 account-currency units. A balance of 1,500 gives a raw size of 0.03 lots before broker constraints. This is a calculation example, not a recommended setting. Check whether the real implementation rounds, floors, caps or uses equity instead.

Apply the symbol’s constraints

A stop-based calculation can use OrderCalcProfit to estimate the result of a price move in account currency. Check the function result and account for costs separately. Align the final size to the symbol’s minimum, maximum and step, then check margin. Leverage affects margin requirements; it does not define the strategy’s sizing formula.

Review the actual volumes

1. Save the formula-related inputs with the report.
2. Inspect several trades after both gains and losses.
3. Confirm that the executed sizes match the intended calculation.
4. Read returns alongside maximum equity drawdown and the full tested interval.

Make it yours with MQLume

With MQLume, you can inspect and customise the sizing logic itself. Explore Quantum Titan MT5 and build a configuration you can explain as well as operate.

Sources and further reading

• OrderCalcProfit
• Symbol volume properties

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