Hi Antenna Masters...

I am going to use a plumber 1/2 copper tubing for a antenna on
372.5MHz.

Using 468/F, I get about 7.5 inches per leg of dipole.

How can I readjust the formula for the 1/2 inch copper?

I read someone that diameter of the tube starts playing a row in the
UHF band.

de KJ4UO

Large diameter elements make the antenna resonant at a lower frequency.
Shorten the elements to resonate at the desired frequency. You'll
probably find that about 7.1" will work well in your case, though
without some test equipment you're likely never going to notice the
difference! Resonance is NOT required for proper operation as an
antenna. An advantage of larger diameter elements is that the useable
bandwidth increases, though again if you're using it on a single
frequency with narrow bandwidth, you'll never notice the effect.

Cheers,
Tom