> 48 inches is the same as 4-feet but that it is also 3-stud-distances long (studs in walls are often placed 16 inches apart).
To some extent that's an artifact of the units we use. We could just as easily put studs 40cm apart, which is approximately the same distance, or 50cm (0.5m) apart, which would be particularly convenient.
From Wikipedia: "In the United States [...] typically placed 16 inches (406 mm) from each other's center, but sometimes also at 12 inches (305 mm) or 24 inches (610 mm)." (https://en.wikipedia.org/wiki/Wall_stud)
A quick search suggests that 400mm is common in metric-using countries.
To some extent that's an artifact of the units we use. We could just as easily put studs 40cm apart, which is approximately the same distance, or 50cm (0.5m) apart, which would be particularly convenient.
From Wikipedia: "In the United States [...] typically placed 16 inches (406 mm) from each other's center, but sometimes also at 12 inches (305 mm) or 24 inches (610 mm)." (https://en.wikipedia.org/wiki/Wall_stud)
A quick search suggests that 400mm is common in metric-using countries.