A method for determining a current spectrum for a circuit design is provided. The method includes determining timing characteristics and power consumption characteristics for the circuit design. From the timing characteristics and the power consumption characteristics a time domain current waveform is constructed. The time domain current waveform is then converted to a frequency domain current waveform. With the frequency domain waveform, one skilled in the art can then identify a location and an amount of decoupling capacitors for a printed circuit board housing the circuit design based on the frequency domain current waveform. A computing system configured to perform the method is also provided.