Terahertz is a unit of measurement sometimes used to measure computer clock speeds. One terahertz is equal to 1,000 gigahertz (GHz), or 1,000,000,000,000 hertz (Hz). Since the majority of personal computers operate between two and four gigahertz, most computer clock speeds are not measured in terahertz. Instead, terahertz is more often used to measure the total speed of computing clusters or supercomputers.
Like gigahertz, terahertz only measures frequency, or cycles per second. Since some processors require more cycles to process instructions than others, terahertz is not always an accurate measurement of overall computing power. Additional factors, such as RAM speed, bus speed, and processor cache, also effect a computer's performance. Therefore, other units of measurements, such as MIPS and FLOPS are typically used to measure the computing performance of supercomputers and other high-end computer systems.