How deep should I sub soil?

Excuse me, I'm in the midst of planning a gardening project and I've come across the question of how deep I should be sub-soiling the soil. I understand that sub-soiling can help with aeration, water drainage, and root development, but I'm not sure exactly how far down I should go. Is there a general rule of thumb for how deep to sub-soil, or does it depend on the type of soil and plants I'm working with? I'd appreciate any insight you can offer on this matter, as I want to ensure that my garden is set up for optimal growth and health.