MT5 lot step and minimum volume: why volume is rejected

Minimum, maximum and step in the symbol specification, how to round a calculated size, and what it does to your records.

Type a lot size that looks reasonable and MetaTrader 5 may answer with an invalid volume message. The cause is usually one of three numbers in the symbol’s specification: the minimum volume, the maximum volume and the volume step. They also shape your journal, because position sizes in your history always land on this grid. This page explains what each number means, how to read them, how rounding works in practice, and what they do to risk and records.

The three numbers

Open the Market Watch window, right-click a symbol and choose its specification. Among the fields you will usually find a minimum volume, a maximum volume and a volume step. Names can differ slightly between builds, so check your terminal. The other fields are covered in the symbol specification guide.

Field	Meaning	Example (hypothetical)
Minimum volume	Smallest order the broker accepts	0.01 lots
Maximum volume	Largest single order accepted	100 lots
Volume step	Increment between allowed sizes	0.01 lots

With a step of 0.01, valid sizes are 0.01, 0.02, 0.03 and so on. A size of 0.015 is not on the grid and is normally rejected. If the step is 0.10, only 0.10, 0.20 and similar sizes are accepted. A cent or micro account type may allow smaller sizes, and the page on account types and your trade history explains why those accounts can look different in the records.

Why a calculated size is often rejected

Position size calculators produce results such as 0.137 lots. The terminal cannot take that, so you must round to the step. Round down if you want to keep risk at or below your limit, because rounding up increases the risk you meant to take. The difference matters more on small accounts, where one step can be a large share of the whole position. The arithmetic and the contract-size side are explained on lot size and contract size, and you can do the calculation on the position size calculator.

Compute the size from your risk limit and stop distance.
Round down to the nearest allowed step.
Check the result is not below the minimum volume; if it is, the trade does not fit your risk rule on that account.
Check the result is not above the maximum volume; very large orders may need splitting, and splitting is visible in the history.

What this does to your records

Because every position size sits on the grid, your history contains a clean list of volumes, and that list is informative. If almost all of your trades are at the minimum volume, you may be sizing by feel rather than by rule. If sizes jump around, check whether each jump was planned. A journal column for planned risk, written in your notes, helps you compare plan and result. The risk side is covered in the risk reward calculator, which can help with the stop and target arithmetic.

An order larger than the maximum volume cannot be sent in one piece. Some traders then send several orders, and on a hedging account each one becomes its own position. The records then show several entries with the same symbol, direction and nearly the same time. The ideas for grouping them with a tag are covered in scaling in and out in the history. AI Trading Journal creates one entry per closed position, so on a hedging account the pieces stay separate unless you tag them. On a netting account the broker merges them into one position.

Partial closes and the step

The step also governs partial closes. If you hold 0.05 lots and the step is 0.01, you can close 0.01, 0.02, 0.03 or 0.04 lots and leave a remainder on the grid. You cannot close an odd fraction. A partial close is recorded as an exit deal for a smaller volume, and the position stays open until the last piece is gone. How those exits appear is covered in partial closes in MT5 history. The app combines partial closes into one entry dated by the last exit on the broker’s server clock.

A worked example (hypothetical)

A trader risks a fixed amount per trade. The calculator suggests 0.137 lots for a given stop. The symbol’s volume step is 0.01, so the trader rounds down to 0.13 lots, which keeps the risk slightly under the limit. Later, with a tighter stop, the calculator suggests 0.004 lots. The minimum volume is 0.01, so the trade cannot be taken within the risk rule at that stop distance. The trader notes this in the journal as skipped because minimum size exceeds risk, which becomes useful data about how account size limits the setups available. All numbers are invented.

Limits and cautions

Minimum, maximum and step values differ by broker, symbol and account type; read your own specification.
The app records closed positions as the server reports them; it does not know what size you planned.
The app is read-only. It never places, modifies or closes a trade, and it does not round or change sizes.
Nothing here is trading advice or a recommended size.

Frequently asked questions

Why does MT5 say invalid volume?

The size is below the minimum, above the maximum, or not a multiple of the volume step. Check the symbol specification.

Should I round lot size up or down?

Rounding down keeps risk at or below your limit; rounding up raises it slightly. The choice is yours, but know which one you made.

Where do I find the volume step?

In the symbol specification in the Market Watch window. Field names can differ by build.

How does the journal treat orders split by maximum volume?

On a hedging account each position is its own entry; tag them to group. On a netting account they merge into one position.

Does the app change my lot sizes?

No. It only reads closed positions.

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