Two traders with identical win rates and R-multiples can end up with very different account trajectories purely because of how they scale position size as the account changes. This is a mechanical, mathematical difference — not a matter of skill.
Fixed Lot (or Fixed Dollar Risk) Sizing
Risk the same dollar amount (or lot size) per trade regardless of account balance changes. Growth is linear: gains and losses are added, not multiplied. This produces a smoother, more predictable equity curve but caps the compounding effect of winning streaks.
Compounding (Percentage) Sizing
Recalculate risk as a fixed percentage of current equity after every trade. Growth is geometric — winning streaks accelerate gains because each trade risks more in dollar terms as the account grows, but losing streaks also decelerate losses in dollar terms as the account shrinks (this is the same mechanism behind drawdown math).
Worked Comparison: 10 Trades, Alternating +2R/-1R
Starting equity $10,000, risk 2% per trade, sequence: W, W, L, W, L, W, W, L, W, L (6 wins at +2R, 4 losses at -1R).
| Method | Ending Equity | Total Return |
|---|---|---|
| Fixed $ risk ($200/trade) | $11,600 | +16% |
| Compounding (2% of current equity) | $11,942 | +19.4% |
Compounding outperforms in this winning sequence because gains occurred on a growing base. Reverse the sequence to front-load losses (L, L, L, W, W...) and compounding underperforms fixed risk instead, because early losses shrink the base that later wins compound from.
The same set of trades in a different order produces different ending equity under compounding. This 'sequence risk' is why compounding amplifies both good and bad luck in the order trades happen to occur.
Practical Guidance
| Situation | Recommended Approach |
|---|---|
| Small account, building track record | Compounding with modest % — lets capital grow meaningfully |
| Funded/prop account with strict drawdown limits | Fixed risk or reduced % near drawdown thresholds |
| Withdrawing profits regularly | Fixed risk on a stable base after withdrawals |
| Large, mature account | Often a hybrid: compound within a capped range, then flatten |
A Common Hybrid Approach
Many experienced traders compound normally but recalculate risk on a step basis (e.g. every $1,000 or 10% of growth) rather than after every single trade. This captures most of the compounding benefit while avoiding wild swings in position size from one trade to the next.