MQL5 Tutorial: Build a Risk Management EA in 50 Lines of Code

Algo Trading Bot — Sun, 17 May 2026 08:44:30 +0000

Risk management is the #1 skill that separates profitable algorithmic traders from those who blow their accounts. You can have the world’s best entry signals, but without proper position sizing, stop losses, and drawdown controls, one bad streak will wipe you out.
In this hands-on MQL5 tutorial, I’ll show you how to build a simple but powerful Risk Management Expert Advisor in under 50 lines of code. It handles:

Dynamic position sizing based on account balance (e.g., risk 1% per trade)
Automatic Stop Loss placement
Daily drawdown limits with trading halt

This EA acts as a safety layer — you can attach it to any chart and use it alongside your strategy or as a foundation for more advanced bots.
By the end, you’ll have a reusable, professional-grade risk module you can expand.

Prerequisites

MetaTrader 5 platform installed
Basic MQL5 knowledge (OnInit, OnTick, trade functions)
A demo account for testing

No prior EA building experience? No problem — this is beginner-friendly but practical for intermediates too.

Core Concepts Behind the EA
Before jumping into code, let’s quickly cover why these features matter:
Position Sizing: Never Risk More Than You Can Afford
Fixed lots are dangerous because they ignore your account size. Risking a fixed percentage (1-2%) of your current balance scales safely and compounds growth.
Automatic Stop Loss
No trade should go without a stop. We’ll calculate lot size based on your desired SL distance in points.
Daily Drawdown Protection
Protect against black swan days. If equity drops by X% in a day, stop trading to preserve capital.

The Complete Risk Management EA Code

//+------------------------------------------------------------------+
//|                                          RiskManagementEA.mq5   |
//|                                  Simple Risk Management EA       |
//+------------------------------------------------------------------+
#property copyright "Your Name"
#property link      "yourblog.com"
#property version   "1.00"

#include <Trade\Trade.mqh>
CTrade trade;

input double RiskPercent = 1.0;        // Risk % per trade
input int    StopLossPoints = 500;     // SL in points (e.g., 50 pips on 5-digit)
input double MaxDailyDrawdown = 5.0;   // Max daily DD % to stop trading
input ulong  MagicNumber = 123456;     // Unique magic

double dailyStartEquity;
datetime currentDay;

//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
{
   dailyStartEquity = AccountInfoDouble(ACCOUNT_EQUITY);
   currentDay = TimeCurrent() / 86400;
   trade.SetExpertMagicNumber(MagicNumber);
   Print("Risk Management EA initialized. Risk per trade: ", RiskPercent, "%");
   return(INIT_SUCCEEDED);
}

//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
{
   // Check new day
   if (TimeCurrent() / 86400 != currentDay) {
      dailyStartEquity = AccountInfoDouble(ACCOUNT_EQUITY);
      currentDay = TimeCurrent() / 86400;
   }

   // Daily drawdown check
   double currentEquity = AccountInfoDouble(ACCOUNT_EQUITY);
   double dailyDD = (dailyStartEquity - currentEquity) / dailyStartEquity * 100.0;
   if (dailyDD >= MaxDailyDrawdown) {
      if (PositionsTotal() == 0) {
         Print("Daily drawdown limit reached. No new trades today.");
      }
      return;
   }

   // Example: Open a sample trade if no positions (replace with your signal)
   if (PositionsTotal() == 0) {
      double lotSize = CalculateLotSize(StopLossPoints);
      if (lotSize > 0) {
         trade.Buy(lotSize, _Symbol, 0, Ask - StopLossPoints * _Point, 0, "Risk Managed Buy");
         Print("Opened buy with lot size: ", lotSize);
      }
   }
}

//+------------------------------------------------------------------+
//| Calculate safe lot size                                          |
//+------------------------------------------------------------------+
double CalculateLotSize(int slPoints)
{
   if (slPoints <= 0) return 0.0;

   double riskAmount = AccountInfoDouble(ACCOUNT_BALANCE) * RiskPercent / 100.0;
   double tickValue = SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_VALUE);
   double tickSize = SymbolInfoDouble(_Symbol, SYMBOL_TRADE_TICK_SIZE);

   double slValue = slPoints * _Point / tickSize * tickValue;
   double lots = riskAmount / slValue;

   // Normalize to broker requirements
   double minLot = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_MIN);
   double maxLot = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_MAX);
   double lotStep = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_STEP);

   lots = MathFloor(lots / lotStep) * lotStep;
   lots = MathMax(minLot, MathMin(maxLot, lots));

   return NormalizeDouble(lots, 2);
}

Total active lines: Well under 50 for the core logic. Clean, readable, and effective.

**## How the Code Works (Line-by-Line Breakdown)
**Inputs Section
Customizable parameters let you tweak risk without recompiling.
OnInit()
Sets up daily equity tracking and magic number.
OnTick()

Resets daily equity on new day
Checks drawdown and halts trading if breached
Calculates safe lots and opens example trades (replace the condition with your own entry logic)

CalculateLotSize()
The heart of the EA. It computes lot size based on:

Desired risk %
SL distance
Symbol tick value (handles forex, indices, metals, etc. accurately)

**Testing Your EA

**
Compile in MetaEditor (F7)
Attach to a chart in MT5 Strategy Tester or live demo
Use different RiskPercent and StopLossPoints values
Monitor the Experts and Journal tabs for logs

Pro Tip: Start with 0.5% risk and 1-2% daily DD limit while testing.

**Enhancements You Can Add Next

**
Trailing Stop functionality
Max open trades limit
News filter integration
Equity-based risk (use balance vs equity)
Partial closes at certain profit levels

These keep the codebase modular and extensible.

**Common Pitfalls to Avoid

**
Ignoring broker specifics (5 vs 3 digits, lot steps) → Always normalize
No drawdown protection → Emotional revenge trading kills accounts
Testing only in trending markets → Use Strategy Tester with real tick data and different conditions
Hardcoding values instead of inputs

**Conclusion: Build Once, Trade Safer Forever