Fixed Fractional Position Sizing: The Safest Method

Risk a fixed fraction of your account on every trade and you can lose 10 times in a row without losing sleep — or your account.

Fixed fractional position sizing is the gold standard for new traders. Instead of betting a fixed dollar amount or a fixed number of shares, you risk a constant percentage of your current account on each trade. As your account grows, your position size grows with it. As it shrinks, your risk shrinks too.

How it works

The formula is simple:

Risk amount = Account balance × Risk%
Position size = Risk amount ÷ (Entry − Stop)

Example: $10,000 account, 1% risk, entry $50, stop $48.

• Risk amount = $10,000 × 1% = $100
• Position size = $100 ÷ ($50 − $48) = 50 shares

Why it's the safest method

Feature	Benefit
Risk scales with account	You can never blow the account with one trade
Auto-compounding	Wins grow position size; losses shrink it
Geometric recovery	After losses, smaller risk prevents a death spiral
Emotionally stable	The dollar loss is always proportional to your wealth

The math of survival

Compare fixed fractional to fixed-dollar risk after a 5-trade losing streak at 1% risk per trade:

Trade	Fixed fractional balance	Fixed-dollar ($100) balance
Start	$10,000	$10,000
After 5 losses	$9,510 (−4.9%)	$9,500 (−5.0%)

Small difference here — but extend it to 20 losses and fixed fractional leaves you with $8,179 versus $8,000 for fixed-dollar, and far less relative risk per trade as you go.

Setting your fraction

• Beginners: 0.5%–1% per trade
• Experienced, validated edge: 1%–2%
• Never exceed 2% unless you fully understand risk of ruin

Use the position size calculator to compute size automatically.

When fixed fractional struggles

1. Small accounts: 1% of $500 is $5 — commissions eat your edge
2. Mixed volatility instruments: Same 1% risk on a 1%-ATR stock and a 5%-ATR crypto produces very different position sizes
3. Withdrawals: If you pull money out regularly, the "fraction" logic breaks

For small accounts, consider fixed fractional on a paper balance you track separately, or top up to a meaningful base.

Rules to make it work

1. Recalculate risk on your current balance, not your starting balance
2. Never round up position size "because it's close"
3. Log every trade in a journal so you can verify your actual risk matched your plan
4. Re-balance weekly, not after every trade — constant tinkering creates errors

Fixed fractional won't make you rich fast. It will keep you in the game long enough to get rich slowly.