Size For Cable Australia - Conduit
So, you would need a conduit with an internal diameter of at least 31.6mm to accommodate the 3 cables with a 30% fill factor.
For circular cables: (or use: Diameter² × 0.7854) conduit size for cable australia
This backend logic demonstrates how to calculate the required conduit size based on AS/NZS standards. So, you would need a conduit with an
import math