Because of their usefulness in carrying out power calculations, listed voltages for power outlets (for example, 120V in the USA, or 230V in Europe) are almost always quoted in RMS values, and not peak values. Peak values can be calculated from RMS values from the above formula, which implies "V" = "V"RMS × , assuming the source is a pure sine wave. Thus the peak value of the mains voltage in the USA is about 120 × , or about 170 volts. The peak-to-peak voltage, being double this, is about 340 volts. A similar calculation indicates that the peak mains voltage in Europe is about 325 volts, and the peak-to-peak mains voltage, about 650 volts.