Commission Impact Calculator
Calculate the impact of trading commissions on net profit from trade size, entry, and exit fees.
Returns commission %, break-even, and annual cost.
Trading commission impact quantifies how much brokerage fees and transaction costs reduce your actual investment returns over time — a critical factor that many retail investors underestimate.
Core formulas: Net Return % = Gross Return % − Total Commission Cost % Break-Even Price (buy) = Purchase Price + (Commission ÷ Shares) Round-Trip Cost = Buy Commission + Sell Commission Annual Drag = Round-Trip Cost × Trades per Year ÷ Portfolio Value × 100
Worked example — stock trade: Buy 100 shares of a stock at $50/share = $5,000 investment. Commission: $9.99 per trade (buy + sell = $19.98 round trip). Stock rises 10% → sell at $55/share = $5,500 gross.
Gross profit = $500 Commissions = $19.98 Net profit = $480.02 | Net return = 9.60% (vs. 10% gross)
Commission drag = $19.98 ÷ $5,000 = 0.40% per round trip
Mutual fund expense ratios — the silent compounding killer:
| Fund Type | Typical Annual Expense Ratio | 30-Year Cost on $100k |
|---|---|---|
| S&P 500 index fund (e.g., FXAIX) | 0.015% | ~$4,500 |
| Average actively managed fund | 0.85% | ~$227,000 |
| High-cost managed fund | 1.5% | ~$370,000 |
The 1% difference: $100,000 invested at 7% return for 30 years:
- No fees: $761,226
- 1% annual fee: $574,349
- Difference: $186,877 — lost to fees
Modern commission landscape: Most US equity brokers (Fidelity, Schwab, TD Ameritrade) now offer $0 commission trades, but hidden costs remain — payment for order flow, bid-ask spreads, and fund expense ratios. Always calculate the true all-in cost before trading.