UA has two different ways:
in "Y" or "B" it is less miles (i.e. 10.000 each way int'l) upgrading to bus
in all other coach (except the very cheap, where no ugrade is possible anyway) you have to double the miles you give in. In any case you'll get upgreded to First on the domestic portion of your flight on two class aircraft

same is for domestic

same is for LH if you give in your U A -M P m i l e s

and same is for