Gross vs. Net Profit: How Broker Commissions & Overnight Swaps Quietly Eat Your Edge

A system that makes +$2 per trade on average sounds like money in the bank, until you learn it costs $3 per trade to run. Gross profit is what the chart gave you; net profit is what survived the trip through commissions, spreads, slippage and financing. The distance between them decides whether most strategies live.

The full cost stack

The 'break-even' system that quietly loses

Do the honest arithmetic on a fast scalping idea: 100 trades, average winner +$6, average loser −$6, win rate 55%. Gross expectancy: 0.55 × 6 − 0.45 × 6 = +$0.60 per trade. Now apply costs: $2 commissions + $1.5 spread/slippage = −$2.90 net per trade. The system that 'wins' 55% of the time loses ~$290 every 100 trades. This is why journals and calculators matter: the futures calculator and stock profit calculator include commissions so the number you see is the number you keep.

Overnight swaps: the fee that bills you while you sleep

Futures don't charge swaps (financing is priced into the contract), but CFDs, forex positions held past 5pm ET and leveraged spot products bill nightly. The sneaky part: swaps are charged on the notional, not on your margin. A $2,000 margin position controlling $100,000 pays financing on the full $100,000.

1. Cost per trade = (total commissions + fees for the month) ÷ number of trades. Most traders have never computed it.
2. Add estimated slippage: compare your intended entry to the fill across 20+ trades, per symbol and per hour. News fills lie differently than quiet-hour fills.
3. Express it in R: if your planned risk is $100 and costs run $6, every trade starts at −0.06R. Small numbers, huge volume.
4. Cost drag = costs ÷ gross profit. If $400 of monthly costs came out of $1,000 gross, execution is eating 40% of the strategy. Below ~15% is healthy; above ~30% usually kills scalps.

When costs choose the strategy

• Breakeven move: target size must clear costs ×2 at minimum. If a round trip costs 2 ticks, 3-tick scalps pay mostly the broker.
• Frequency is a cost multiplier. Swing traders pay the same stack but divided over fewer trades and bigger targets, that's why high-frequency edges are so rare for retail.
• Zero-commission isn't free. No-commission brokers earn through wider effective spreads (payment for order flow). Compare total fill quality, not the sticker price.

Trading cost vocabulary cheat sheet

Trading fees, explained like you're five

Forget the fee schedules for a minute, this whole problem is one arcade day.

The arcade card

Imagine your parents buy you an arcade card loaded with $20. Every game takes a coin from the card, and every prize you win adds tickets to it. At the end you cash out and count what you got. Three magic terms:

• Gross profit: the tickets you won, what the games 'gave' you.
• Costs: the coins the card lost for every game you played, plus the entrance stamp they charged at the door.
• Net profit: tickets left minus coins spent, the prize you can actually take home.

Why this is dangerous

Now imagine you played 50 games and won a prize in 30 of them. Sounds like a great day, right? Two ways the arcade wins anyway:

• The mistake many make: they count 30 wins and forget the 50 coins spent to play. 'I won 30 times!' means nothing when each play cost more than each prize was worth.
• The reality: small per-game fees are invisible one at a time and enormous in a pile. The arcade doesn't need to win your games, it just needs you to keep playing.

Costs are exactly why one-trade math stops being enough, the stock & contract profit guide shows how ROI changes once every fee is counted.