MQL4 ERR_INVALID_TRADE_VOLUME
MQL4 error 131 invalid trade volume maps to ERR_INVALID_TRADE_VOLUME: invalid trade volume. The requested lots violate the symbol minimum, maximum, step, or another broker volume rule. Capture GetLastError immediately after the failed call, correct the cause, and retry only when the condition can change.
Open the Coding Agent, then choose MQL4 from the language menu.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}The official MQL4 runtime table names error 131 ERR_INVALID_TRADE_VOLUME and defines it as “invalid trade volume.” The requested lots violate the symbol minimum, maximum, step, or another broker volume rule.
The error number is evidence about one failed call, not a diagnosis of the whole EA. Read the API sentinel first, then call GetLastError immediately because that function returns the current _LastError value and resets it.
Start with the inputs and external state that existed at the failure point. A later log entry or a successful call can overwrite the useful context.
Recalculate the volume once from current symbol properties. Do not repeatedly resend the same invalid lots or round upward beyond the risk budget.
Keep the original trading and risk rules intact. A workaround that widens stops, increases volume, changes an account setting, or ignores a failed return value can hide the symptom while changing the system.
| Check | Action |
|---|---|
| Lots are below MODE_MINLOT or above MODE_MAXLOT | Clamp only within the strategy limit and reject values outside the broker range. |
| Lots do not align with MODE_LOTSTEP | Round volume down to the current symbol lot step. |
| Floating-point rounding produces an unsupported volume | Normalize the result to the precision implied by the lot step. |
| The EA applies one symbol’s lot rules to another symbol | Read min, max, and step for the order symbol at the decision point. |
The script logs the submitted lot size with the failed OrderSend call. Production code should calculate a valid step-aligned volume before reaching this request.
The example improves validation and logging. It does not prove the operation will be accepted by a broker or behave safely in live trading.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}Pineify can generate or revise one self-contained .mq4 file with MQL4-specific reference context. Its independent static checker returns MetaEditor diagnostics so you can repair source issues before testing in your own MT4 environment.
Open MQL4 Coding AgentStatic diagnostics do not prove runtime behavior, backtest results, broker compatibility, or live-trading safety.
Check the API return value before interpreting an error number from the log.
Call GetLastError immediately and record error 131, symbol, prices, volume, ticket, and terminal state relevant to the operation.
Clamp only within the strategy limit and reject values outside the broker range.
Compile the revised source, then test with the same MT4 build, broker, symbol, account permissions, and market state.
ERR_INVALID_TRADE_VOLUME means invalid trade volume. The code should still identify which API returned failure and log the inputs used for that call.
Lots are below MODE_MINLOT or above MODE_MAXLOT Lots do not align with MODE_LOTSTEP Floating-point rounding produces an unsupported volume The EA applies one symbol’s lot rules to another symbol
Recalculate the volume once from current symbol properties. Do not repeatedly resend the same invalid lots or round upward beyond the risk budget.
It reports the current _LastError value and resets it. Other operations can change the error state, so a delayed read may describe the wrong call.
Pineify can revise a self-contained .mq4 file, add validation and error logging, and return static MetaEditor diagnostics. It cannot prove broker acceptance, account permissions, market availability, or live execution.
Last verified against the linked official references on . Compile and test the final source in the MetaTrader 4 build, broker, symbol, and account environment you plan to use.
Define the requirement, inspect the generated source, repair diagnostics, and test the behavior in your own MT4 environment.
Open Coding Agent