Water Supply Sizing

Ok...here's the situation. I have put an addition on my house ading 800 sq ft. Included in this is 1 new bath containing a water closet, lav, tub/shower combo, and it's on the second floor. The existing bathroom and kitchen were more than adequate as far as pressure,volume etc..Now, my situation is this..with the new bath, I have exceeded the wsfu for the existing 3/4" supply's. What I would like to do is increase to 1 inch from the meter to the hot water heater, and at least the first floor bathroom group. All the remaining supply's will be 3/4" reduced to 1/2". My question is this, do I just reduce the 1" to 1/2", the same as you would with 3/4", to supply the fixtures, or do I need to reduce to 3/4 for x amount of feet then 1/2". Also how much 1/2" do you advise to use to supply the fixture, once reduced. I've heard 5'

Any help or advice would be greatly appreciated

The best way is to size the pipe backwards toward the meter,
They are branches of a tree, that get thicker toward the trunck.

Water pipe sizing

UPC Chapter 6 on water supply