The math behind it
On raw or ECN accounts the quoted spread is lower but you pay a commission per lot. Compare spread plus commission, not spread alone.
An example with numbers
EUR/USD is quoted 1.08502 / 1.08514: a spread of 1.2 pips. Trading 2 standard lots costs 1.2 × $10 × 2 = $24 per round trip.
If a scalping backtest on mid prices showed +0.15R per trade, the spread alone takes 0.12R of it, 80% of the edge. The swing trader pays a quarter as much per unit of risk. Same broker, same spread, completely different impact.
Mistakes to avoid
- Forgetting charts show the bid. A short's stop is hit by the ask, which can be above the highest candle you see.
- Trading through rollover. Spreads can widen sharply for a few minutes around the daily reset.
- Comparing accounts on spread only. Add the commission per lot to get the real cost.
What the journal does with it
The journal tracks Total Commission, Commission % of Gross P&L and Net P&L After Commission. Synced accounts carry the broker's own figures, so the cost of trading shows up as a number rather than a feeling.
See your own Spread from real trades
Stop estimating it in a spreadsheet. Log or sync your trades and the journal keeps the number current after every close.
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