# How to Set Lot Size: Money Management Rules That Work
Your Lot Size is the Difference Between Survival and Liquidation
Most beginner traders obsess over which trades to take. They miss the real point: how much money you risk per trade decides whether you're still trading in a year or broke in three months. Lot size is your first and most powerful defense against the market.
In funded accounts and copy trading with MetaTrader or any platform, lot size isn't a suggestion—it's the law. Your prop firm gives you capital, but you're responsible for managing it. Without disciplined lot sizing, your account closes before you've learned anything.
Rule #1: Risk Per Trade (% of Account)
The golden rule: never risk more than 1–2% of your account per trade.
Live example:
- Account: $10,000
- Risk per trade: 1% = $100
- Your stop loss: 50 pips
- Lot size needed: 100 ÷ 50 = 2 standard lots (EUR/USD)
This rule keeps you alive. Lose 10 trades in a row at 1% risk per trade, and your account drops to $9,043—not zero. You have room to learn, adjust, and come back.
Risk 10% per trade (common mistake), and a losing streak wipes you out in weeks.
Rule #2: Adjust Lot Size for Account Type
Trading your own money is different from trading a funded account. The rules shift.
Personal accounts:
- 1–2% risk is standard
- Freedom to adjust based on your psychological tolerance
Funded accounts / prop firms:
- Respecting daily loss limits is mandatory, not optional
- Track your total accumulated loss across the entire challenge
- Size every lot so a single trade cannot break your daily or total loss limits
- Use a risk manager (like Guardian, within Onyx) to block trades before you violate rules
For example, if your challenge allows -$500 daily loss and you have 5 open trades with 50-pip stops, your max lot size is capped. A single bad trade shouldn't liquidate your challenge alone.
Rule #3: Use a Simple Formula
Lot size = (Account × Risk %) ÷ Stop loss in dollars
Or more directly:
Lot size = Money I want to risk ÷ (Stop distance in pips × Pip value)
On EUR/USD with standard lots, 1 pip = $10 per standard lot.
If you want to risk $50 and your stop is 100 pips:
- $50 ÷ (100 × $10) = 0.5 standard lots
Simple. No emotion. No guessing.
Rule #4: Never Increase Lot Size After Losses
It's the opposite of what most losing traders do. After losing money, they feel pressure to recover fast, so they increase lot size. That's the express route to ruin.
If you lose, reduce your lot size or take a break. If you win, reinvest only the profits, not your emotional need to recover.
In funded accounts, a losing streak is never an excuse to break your daily limit. It's a reason to be more conservative.
Rule #5: Calculate Lot Size Before Opening Any Trade
Never open a trade without knowing exactly:
- Where your stop loss sits (in pips)
- How much money you're risking
- What lot size results from that risk
If the math doesn't fit within your daily or total loss limits, don't trade. Wait for the next opportunity.
This is real discipline, not fear. A professional trader exits the idea if proper risk management won't allow entry.
Tools That Help You
You don't have to do math in your head. Onyx includes a built-in lot size and risk calculator right on the platform. Enter your capital, stop distance, risk %, and it calculates your lot automatically.
Plus, Guardian (the risk manager inside Onyx) monitors your daily and total loss limits. If you try to open a trade that breaks your rules, it blocks you before it happens.
That's critical if you're trading a funded account: you can't break the firm's rules. Guardian helps you follow them automatically.
The Real Secret of Money Management
Correct lot sizing is boring. It's not sexy. It doesn't promise you $10,000 this month. But it's the difference between a trader who survives five years and one who burned out their account in three months.
Money management isn't flashy, but it's what separates winners from losers.
Start today: calculate your 1% risk, apply the formula, and let Guardian protect your capital. The rest is execution.