Kilt size question

[Bugbear]

It isn't too difficult to measure that and get a fairly close idea of how many yards are in a kilt. Each pleat should be pretty much the same size, except for the first and last.
Measure the pleat size from inside crease to inside crease on a few of the back pleats at the bottom of the kilt to get an idea of what length of fabric is in each one.
Then multiply that length by the number of pleats.

Add that number to the measured width of the apron and width of the underapron at the bottom of the kilt, and that should be about how many yards are in your kilt.
It is unlikely that it is exactly eight yards or six yards.

Hope that helps.