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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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