An apparatus for calculating power consumption includes a behavioral synthesis unit for generating a clock-level description by behavioral synthesis of an algorithm description; a clock-level simulation unit for simulating a clock-level description and calculating operating ratios of storage elements and arithmetic units indicated by the clock-level description; a storage-element power calculation unit for calculating a predicted value of power consumption of a storage element portion based upon a power calculation formula, which has been read out of a power-calculation-formula file, and the operating ratios of the storage elements; and a combinational-circuit power calculation unit for calculating a predicted value of power consumption of an arithmetic unit portion based upon a power calculation formula, which has been read out of the power-calculation-formula file, and the operating ratios of the arithmetic units, and calculating a predicted value of power consumption of a combinational circuit, with the exception of arithmetic units, based upon a power calculation formula, which has been read out of the power-calculation-formula file, the operating ratios of the storage elements and arithmetic units and the operating ratios of input/output ports.