What hole size is recommended for 10/2 in floor joists?

I usually drill 5/8" holes for 14/2 and 12/2 wiring. I think 10/2 wiring
fits too, but it has been a while since I wired our house. You could easily
switch to 3/4" if needed. Basically, the hole should be big enough for the
wire to pass through easily without binding or damaging the cable sheath.
Anything bigger just weakens the joists/studs.

Still, if you have lots of wiring to run, it's easier to drill a bunch of
equal sized holes, even if you're running different cable sizes. This also
lets you buy a good quality self-feeding auger bit, instead of a bunch of
cheap bits in multiple sizes.

I only run one cable through each hole and try to space multiple holes at
least 4" apart (center to center). Try to drill your holes in the center of
the joist (vertically) when possible, and never near the upper or lower two
inches. Space multiple holes along the length of the joist, not on top of
each other vertically.

Anthony