According to an embodiment, a cell state calculation apparatus includes the following elements. The database stores a function indicating a relationship between a voltage and a charged capacity of an active material. The active material amount calculation unit calculates an amount of an active material of the secondary cell by referring to the database and by using the voltage detected by the voltage detector and the current detected by the current detector while the secondary cell is charged or discharged. The open circuit voltage calculation unit calculates a function indicating a relationship between an open circuit voltage and a charged capacity of the secondary cell by referring to the database and by using the calculated amount of the active material.
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