What is the minimum lot size in MT5?

The minimum lot size in MT5 is the smallest volume your broker accepts for a symbol, often 0.01 lot on forex pairs. It comes with a volume step, the increment every order size must follow: with a 0.01 step, 0.13 lot is valid and 0.135 lot is not.

MT5 lists both in the symbol’s Specification window as Minimal volume, the “minimal volume of a deal for the symbol”, and Volume step, the “volume change step”, next to Maximal volume and, where the broker sets one, Volume limit (MT5 help: Market Watch). An Expert Advisor reads them as SYMBOL_VOLUME_MIN, SYMBOL_VOLUME_STEP and SYMBOL_VOLUME_MAX (MQL5 symbol properties).

Common minimum lot sizes in MT5

These are common, not universal. Read your own broker’s values for each symbol: right-click it in Market Watch (Ctrl+M) and choose Specification.

Why a correctly sized trade can be too small

Risk-based sizing produces an exact number that rarely lands on a volume step, so it is rounded down to keep the loss at the stop loss within the amount set. When the exact size is smaller than the minimum lot, rounding down gives zero, and the smallest order that exists risks more than planned.

Staying within 1% then leaves two outcomes: a closer stop, where the trade idea allows one, or no trade. Lot size for a $100 account works through the numbers for small balances, and the position size calculator shows the rounded size and the real loss for yours.

Common mistake: rounding to the nearest step

Rounding to the nearest step sometimes rounds up. With $50 at risk and a $7.50 gold stop at 100 oz, the exact size is 0.0667 lot: 0.07 lot loses $52.50 and 0.06 lot loses $45.00. Only rounding down stays inside the limit.

A size that is not a whole number of steps is not accepted at all. The trade server answers with return code 10014, TRADE_RETCODE_INVALID_VOLUME, “Invalid volume in the request” (MQL5 return codes). MQL5’s list of checks a trading robot must pass before publication in its Market includes checking the volume against the minimum, the maximum and the step before the order is sent (MQL5 article).

How PipWarden handles the minimum lot

PipWarden sizes each trade from your risk per trade and the stop distance, using the tick value your broker reports, then rounds down to the broker’s volume step and caps the result at your maximum lot and the broker’s maximum volume. If the result is below the minimum lot, the trade is skipped and logged as “Risk below minimum lot”. The risk is not raised to fit. Why an EA is not taking trades covers this and the other skip reasons, and the features page lists every check.