How many packing cubes do I actually need?

For a typical one-week carry-on trip, most reviewers we read settle on 3 to 4 cubes: one large for shirts, one medium for pants, one small for underwear and socks, and sometimes a separate pouch for accessories. Larger 8- to 10-piece sets are popular because they include toiletry pouches and shoe bags, but several r/onebag commenters note the biggest cube in those sets is often too large for carry-on luggage.