Jason Young wrote:

I am trying to layout the floorplan for a bathroom remodel. The bathroom
had a tub & standalone shower. My question is if I can swap uses for the
drains, using the old shower drain for the tub, and the old tub drain for
the shower?

I would think this would be a nobrainer, but since I'm new to the world
of plumbing, I thought I'd get some opinions...

Thanks,
Jason

Technically, the shower should be 2" and the tub 1 1/2".
As a practical matter, it won't matter but you'll have to adapt
for the different sizes. Of course, you'll have to watch the
elevation of the trap(s).
Jim