  In this talk we discuss a number of ChPT calculations relevant for lattice
QCD. These include the finite volume corrections at two-loop order for masses
and decay constants. The second part is about hadronic vacuum polarization
where we present the two-loop ChPT estimate for the disconnected and strange
quark contributions. We also present the finite volume corrections at two-loop
order. The final part is the one-loop finite volume with twisted boundary
conditions contribution to $f_+(q^2)$ and the full $K_{\ell3}$ amplitude
