The low rate (C/33) discharge data obtained from a calendar life study were numerically analyzed with a single particle model. The simulation showed that the stoichiometric window for the cathode shrank with capacity fade. The change of the stoichiometric window for the anode was more complicated. The aged anode became less charged when the capacity fade was caused mostly by the loss of cyclable lithium ions. The anode would be charged to a higher stoichiometric number (or state of charge, SOC) when the capacity fade became controlled by the loss of active material in the anode.