I once bought 2cm thick hemp rope for reenactment purposes (can’t recommend, it’s worse than nylon and costs more and maintaining it sucks).

I don’t have any spare, but I chucked some on a scale, and it seems to be about 250 grams per meter, for about 8.5lbs per 50ft.

So D&D rope is even thicker, or its tarred (which you absolutely should do if you dislike drying rope).