I don't have an interior gauge, just the one on the tank.
when I was newer, i was shocked at how little propane was actually used...I don;t think I've ever used more than a 1/2 tank during one of our typical month long summer trips.
a little hot water for the dishes, fridge when we are off shore power ( about 1/3) and a maybe 30 ~40 minutes of burner time a day
there is a hot water trick to checking level without a gauge:
https://www.thekitchn.com/grilling-t...f-water-176349