Spread as a share of average range is the filter nobody uses

[Amanhasnoname]

A 1 pip spread sounds fine until it is compared with how much the pair actually moves. If the average 5 minute range is 4 pips, that spread takes a quarter of the typical swing. If the range is 12 pips, the same spread is under 10 percent.

That ratio changes through the day. At 3 am New York time on EURUSD, ranges may shrink to 2 or 3 pips per 5 minutes while spreads stay near the usual level. At the London open, the same pair can move 10 pips in the same window.

Tracking the ratio turns a vague feeling into a rule. A simple example would be skipping any trade where the current spread exceeds 15 percent of the recent average range. Anyone testing this will quickly see which hours and pairs clear the bar and which never do.

The filter also adapts automatically to news, rollover, and holidays without needing a calendar, because spreads and ranges both respond to conditions in real time.

What spread-to-range threshold seems reasonable for scalping, and has any rule like this ever been tested properly?