Re all those conversions....
At some point now lost in the mist of time, an inch was defined as being exactly 25.4 mm, with no further figures behind the decimal point.
Hence a foot is also exactly 0.3048 m.
The "inverse" conversion factors are not exact, so you're always doubtful about the precision of the result. That may not matter much in a discussion about altitude, but it can matter when dealing with aircraft components!