What power scale is Ichigo?

Ichigo is scaled to 5-C at least for: Tanking Yhwach’s Casual Attacks. Yhwach Stating he has no room for error against Ichigo/Him having a Fearsome Bankai.

What is Ichigo’s full power?

Since Ichigo has achieved the full power of his bankai, his appearance changes as well. A horn juts out of his left temple, one of his eyes glow yellow, and two black stripes run down his face. This form mirrors that of the Tensa Zangetsu he fought during Jinzen, an obvious foreshadowing of his true nature.