Direct answer: Position sizing is simple math: divide your risk per trade by your stop distance to get share count. But most traders skip the math and blow up. This article gives you the 3 numbers to set before every trade—and a formula that takes 30 seconds.
Educational only, not financial advice.
Every blown account has the same story: size too big, emotions too high, no plan when things went wrong. Position sizing fixes that—if you actually do it.
Reality check: If you've never calculated your position size before entering, you're gambling. The math takes 30 seconds. Skipping it costs accounts.
The 3-Step Sizing Process
Before you enter any trade, you need exactly 3 numbers written down:
1. Max Loss Per Day
This is your circuit breaker. Hit this number, you're done for the day.
Rule: Don't lose more than 2-3% of your account in a single day.
If your account is $25,000:
- 2% max daily loss = $500
- 3% max daily loss = $750
Pick one. Write it down. When you hit it, close everything and walk away.
2. Risk Per Trade
This is how much you're allowed to lose on a single trade.
Rule: Risk 0.5-1% of your account per trade.
With a $25,000 account:
- 0.5% risk per trade = $125
- 1% risk per trade = $250
If you risk 1% per trade with a 3% daily max, you get 3 losing trades before you're stopped out for the day. That's your buffer.
3. Stop Distance
This is the price difference between your entry and your invalidation point.
Rule: Your stop goes at invalidation—where your thesis is wrong. Then you calculate size.
If you're entering at $50.00 and your invalidation is $48.50:
- Stop distance = $1.50 per share
This number comes from your trade setup, not from how much you can afford to lose.
The 30-Second Position Size Formula
Once you have your 3 numbers, the formula is simple:
Position Size = Risk Per Trade ÷ Stop Distance
Example 1: Normal Setup
- Account: $25,000
- Risk per trade: 1% = $250
- Entry price: $45.00
- Stop price: $43.50
- Stop distance: $1.50
Position size: $250 ÷ $1.50 = 166 shares
Total position value: 166 × $45 = $7,470 (about 30% of account)
You're using 30% of your account but only risking 1%. That's the point.
Example 2: Wide Stop
- Account: $25,000
- Risk per trade: 1% = $250
- Entry price: $120.00
- Stop price: $115.00
- Stop distance: $5.00
Position size: $250 ÷ $5.00 = 50 shares
Wide stop = smaller position. The math adjusts automatically.
Example 3: Tight Stop
- Account: $25,000
- Risk per trade: 1% = $250
- Entry price: $22.00
- Stop price: $21.50
- Stop distance: $0.50
Position size: $250 ÷ $0.50 = 500 shares
Tight stop = larger position. Same risk, different size.
Log your sizing decisions in your trading journal so you can spot patterns over time.
The 3-Number Sizing Card
Write this on a sticky note and put it on your monitor:
My Sizing Rules:
✓ Max loss/day: $____
✓ Risk/trade: $____
✓ Formula: Risk ÷ Stop Distance = Shares
Fill in your numbers based on your account size. Don't trade without checking them.
Checklist
Position Sizing Pre-Trade (30 seconds):
✓ I know my max loss for today
✓ I know my risk per trade in dollars
✓ I have a stop price from my setup (not from my P&L)
✓ I calculated: Risk ÷ Stop Distance = Shares
✓ This position doesn't exceed my daily max if it loses
✓ I wrote the size down before entering
Why Traders Skip This (and Blow Up)
The math isn't hard. But traders skip it for predictable reasons:
"I'm confident in this one." Confidence isn't a sizing method. The setup that looks best can still lose.
"The math is too slow." It takes 30 seconds. You'll spend hours recovering from one oversized loss.
"I'll just use the same size every time." If your stop changes, your size must change. 100 shares with a $0.50 stop is not the same risk as 100 shares with a $2.00 stop.
"I want to make back what I lost." This is revenge trading. It's the fastest way to turn a bad day into a blown account.
Common Mistakes
- Sizing based on conviction, not math — Every setup can lose
- Same share count regardless of stop distance — Wide stops need smaller size
- No max daily loss rule written down — One bad day ruins the month
- Increasing size after wins — You give it back on the next loss
- Placing stop based on dollars, not structure — Stop goes at invalidation first, then calculate size
- Never recalculating as account changes — Update your numbers monthly
Sizing Drift: The Silent Account Killer
Most traders don't blow up in one trade. They drift.
- Win a few → size up "because it's working"
- Lose one → size up "to make it back"
- Repeat until account is gone
Use trade review to spot sizing drift before it kills your account. Look at your average size over the last 20 trades. Is it creeping up?
Do This Next
- Calculate your 3 numbers right now (max loss/day, risk/trade, stop distance for your typical setup)
- Write them on a sticky note and put it on your monitor
- Use the formula on your next 5 trades—no exceptions
Track your sizing with TraderNSYT and let Flo flag when your position sizes drift from your rules. Build execution consistency by following your sizing rules on every trade.
Related Reading
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