We present lattice QCD calculations of the hadronic light-by-light (HLbL) contribution to the muon anomalous magnetic moment with physical masses at two different lattice spacings. The calculation includes all connected diagrams and the leading, quark-line-disconnected diagrams. Our first calculation has been performed on the $48^3\times 96$ ensemble generated with physical quark masses, $a^{-1}=1.730(4)$ GeV, and $L=5.476(12)$ fm spatial extent by the RBC and UKQCD collaborations using mobius domain wall fermions. We find $a^{\rm HLbL}_\mu=5.35(1.35)×10^{−10}$, where the error is statistical only. We present similar, preliminary results on a companion ensemble with $a^{-1}=2.359(7)$ GeV and the same spatial extent, and compare the size of non-zero lattice spacing effects between the two.

Hadron Structure