Often I weigh myself with the pack on as I am about to leave home . Than I subtract my weight (plus clothing worned) to get what I have on my shoulders.
At the trailhead I add water (usually 1 to 2L) .
On my last 6 day trip I had just under 12kg ,( 26.4 lbs) , that would take me down to around 30f comfortably (food and gear)
I find it a bit peculiar when people rave on about how light their "..." is but in reality they HAVE to have a book or two, a bottle of whisky or other stuff never included in the original weight.
Again what matters to me is the total weight on my shoulders not on a spreadsheet.
Franco