Calculate Real Maximum Lot


Hi guys,

I'm #C programmer and I start to design a new project in #MQL5.

Has anyone been able to calculate the exact amount of the #maximum #lot in #MQL5?

I used This Function But Sometimes Happened   Error "Not Enough Money" .

I think Some other parameters are also effective in determining it.

Thanks a lot ...

//| Calculate Maximum lot size                                       |
double Get_Lot_Maximum(ENUM_ORDER_TYPE type)
   double price=0.0;
   double marginlot=0.0,margin=0;
//--- select lot size
   //double lot=NormalizeDouble(AccountInfoDouble(ACCOUNT_marginlot_FREE)*MaximumRisk/marginlot,2);
   double lotmax=AccountInfoDouble(ACCOUNT_MARGIN_FREE)*MaximumRisk/marginlot;
   if(!OrderCalcMargin(type,_Symbol,lotmax,price,margin)) return(0.0);
   Print(EnumToString(type),"    marginlot= ",marginlot,"   lotmax= ",lotmax," margin= ",margin);
   return lotmax;
William Roeder  

Risk depends on your initial stop loss, lot size, and the value of the symbol. It does not depend on margin and leverage. No SL means you have infinite risk. Never risk more than a small percentage of your trading funds, certainly less than 2% per trade, 6% total.

  1. You place the stop where it needs to be — where the reason for the trade is no longer valid. E.g. trading a support bounce the stop goes below the support.

  2. AccountBalance * percent/100 = RISK = OrderLots * (|OrderOpenPrice - OrderStopLoss| * DeltaPerLot + CommissionPerLot) (Note OOP-OSL includes the spread, and DeltaPerLot is usually around $10/pip but it takes account of the exchange rates of the pair vs. your account currency.)

  3. Do NOT use TickValue by itself - DeltaPerLot and verify that MODE_TICKVALUE is returning a value in your deposit currency, as promised by the documentation, or whether it is returning a value in the instrument's base currency.
              MODE_TICKVALUE is not reliable on non-fx instruments with many brokers - MQL4 programming forum 2017.10.10
              Is there an universal solution for Tick value? - Currency Pairs - General - MQL5 programming forum 2018.02.11
              Lot value calculation off by a factor of 100 - MQL5 programming forum 2019.07.19

  4. You must normalize lots properly and check against min and max.

  5. You must also check FreeMargin to avoid stop out

Most pairs are worth about $10 per PIP. A $5 risk with a (very small) 5 PIP SL is $5/$10/5 or 0.1 Lots maximum.