How deep is deep enough? Where’s the bottom? Why does everyone’s squat position look different? Confusing stuff, but it shouldn’t be—here’s how it works.
Full depth in a squat is closing the knee joint as much as possible without losing the proper extension of the back while maintaining balance over the foot. That’s it.
If you sit all the way down and relax your trunk, your hips will sit a bit lower, but you’re now in a compromised position that you don’t want to load.
Set your back properly and the hips will rise slightly, but this is maximal depth in a practical sense—this is as low as you can squat with a sound structure for loading.