A remaining capacity calculation method for a secondary battery and a battery pack are provided. Dischargeable electric power is accurately calculated and accuracy of a remaining capacity rate found by an electric power integration method may be improved by providing a remaining capacity calculation method for a secondary battery. The method includes calculating a consumed electric power by way of integration of voltage and current measured at a preset time interval when using the secondary battery; calculating an available dischargeable electric power by subtracting an energy loss and unavailable energy from a discharge electric power of the secondary battery; and calculating a remaining capacity rate from a ratio between the calculated electric power and the dischargeable electric power.