Commission rounding on micro lots: the cents that add up
Posted: Thu Oct 29, 2026 4:05 am
Commission is often quoted per standard lot, like seven dollars per round trip. On micro and mini sizes, rounding rules can change the true cost in ways that are easy to miss.
Some brokers round commission up to the nearest cent per side, others charge a minimum per ticket, and a few apply the same rate regardless of size. A 0.1 lot trade might pay a commission closer to one and a half times the proportional amount.
On a small account running dozens of trades per day, that rounding can add a noticeable drag. A strategy with a theoretical edge of 0.4 pips per trade after costs can drop to nearly zero once the rounding is counted.
The fix is simple but tedious. Check the real commission on a few different lot sizes and compare against the published rate. Then use the actual figure in expectancy calculations.
Worth asking around: have you compared the actual commission charged on small lots to what the broker's price list suggested?
Some brokers round commission up to the nearest cent per side, others charge a minimum per ticket, and a few apply the same rate regardless of size. A 0.1 lot trade might pay a commission closer to one and a half times the proportional amount.
On a small account running dozens of trades per day, that rounding can add a noticeable drag. A strategy with a theoretical edge of 0.4 pips per trade after costs can drop to nearly zero once the rounding is counted.
The fix is simple but tedious. Check the real commission on a few different lot sizes and compare against the published rate. Then use the actual figure in expectancy calculations.
Worth asking around: have you compared the actual commission charged on small lots to what the broker's price list suggested?