This error can happen for different reasons.

Option 1 #

One is that your lot size is too small and the rounding becomes 0 or smaller than the minimum lot size.
In that case, you will see an error similar to this:

Trade lot size too small or not enough margin Lot size = 0.00 Free margin = -10000000000.00

In this case, your calculated lot is rounded down to 0 or smaller than the minimum lot size allowed by the broker.

This means one or more of the following:

• Your account size is too small.  
• Your risk per trade is too small for the account.  

If your account size is too small or your risk per trade is too small, the number of points of the stop loss will result in a calculated lot size that is rounded down to 0. In this case, the solution can be to increase your risk per trade or your account size.

This tends to happen more with swing trading strategies or strategies that have large SL sizes in points/pips. As a general rule the larger the SL size the lower the lot size that will be calculated, which can result in these cases.

Option 2 #

Another way in which error can present itself is in the form of not enough margin such as this error:

Trade lot size too small or not enough margin Lot size = 1.67 Free margin = -1801.84
Note: In this example the account size is 3500

As you can see in the error message the “Free margin” is negative meaning that there is not enough margin in the account to open said lot size.

This usually means that your account leverage is not large enough to open the trade size.

The solution to this is to decrease the risk per trade or position sizing used so that the calculated lot size can be opened with the available leverage. In the example above reducing the risk per trade to half ( from 1% to 0.5%) would allow for the trade to be open assuming that there are no other trades open in the account and that the account has 30x leverage.
Alternatively, if the account were to increase its available leverage to 50x or 100x this error would also be solved without needing to modify the risk per trade.

As opposed to the previous error, this error tends to happen due to position size being too large or leverage being too small and it tends to happen with strategies that trade in smaller timeframes or that in general have smaller SL sizes. The smaller the SL size the higher the calculated lot size when using a fixed %, or $ risk per trade which can lead to lot sizes that are too large for the account.

Option 3 #

The error can sometimes show the same values or behavior but have a completely different reason. Such is the case of the following example:

Trade lot size too small or not enough margin Lot size = 0.00 Free margin = -10000000000.00

This error can be accompanied by other behavior such as those described by one of our members in the slack channel:

This error can happen in some cases due to the broker feeding wrong information or incomplete information to MT4. It can also be caused due to the EA being applied to a non-tradable symbol.

In this case, the solution will depend on many different factors but the most common solution is to check with your broker which are the tradable symbols and if some symbols have trading restricted or are used only for reference.

In the example shown in the screenshot, the solution was to apply the EA to the symbols with the suffix “.r” as those are the tradable instruments by the broker our member was using.