How many yards for a belted plaid

[Robinhood]

I've searched the archives to find the correct
length for a belted plaid, and all I have found
is between 4 and 6 yards. I'd like to know
how to decide where in this range is the proper
size.

It seems that a mere 4 yards is enough length
to pleat for all but the largest waistlines. I'm
therefore wondering if the choice of length
is determined by factors like height or arm
span, or shoulder width, which may make a
difference in the fit of the upper portion of the
plaid.

Maybe height is a factor in having a blanket
long enough to sleep under (or in) when it
is not being worn.

Can anyone say with any authority how
to tell what length is correct?