calculator program

[Jude DaShiell]

How do you convert 450 millimeters into inches?  I'm not even going to ask 
how to compute a hypotenuse with it, I'll not be hurt for the conversion 
my cell phone can do it.  I was doing all of this math to figure the 
screen display measurement area and those are hypotenuse calculations 
every time.  I need to know that since I'm trying to get Xwindows properly 
started up on debian.