We derive a quantum gravity boundary mass from the D3 information-erasure framework by setting the per-bit D3 displacement equal to the Schwarzschild radius: M_QG = m_P·√(ln2/8π) = 0.166071 m_P. Below this mass, each bit erased costs more than the entire Schwarzschild radius — classical GR breaks down. The ratio D3/r_s obeys an exact power law: D3(M)/r_s(M) = (M_QG/M)², yielding exact integers at rational mass fractions. The Kerr extension gives M_QG(χ) = M_QG·√(f(χ)). At χ→1, M_QG→0. All results verified to ten significant figures. This completes the D3 research series (Papers 1–5).