Million instructions per second (MIPS) is a measure of a computer's processor speed. However, this measure is useful only among processors with the same instruction set, as different instruction sets often take different numbers of instructions to do the same job. Many reported MIPS values have represented 'Peak' execution rates on artificial instruction sequences with few branches, whereas realistic workloads consist of a mix of instructions, some of which take longer to execute than others. The performance of the memory hierarchy also greatly affects processor performance, an issue not considered in MIPS calculations. Because of these problems, researchers have created standardized tests such as SpecInt to measure the real effective performance in commonly used applications, and raw MIPS has fallen into disuse. It was even pejoratively referred to as "Meaningless Indication of Processor Speed", or "Meaningless Information Provided by Salespeople". In Linux and UNIX circles, they are often referred to as 'bogoMIPS'.

The floating-point arithmetic equivalent of MIPS is FLOPS, to which the same cautions apply.

In the 1970s, minicomputer performance was compared using VAX MIPS, where computers were measured on a task and their performance rated against the VAX 11/780 that performed a nominal 1 MIPS. (The measure was also known as the "VAX Unit of Performance" or VUP).

Most 8-bit and early 16-bit microprocessors have a performance measured in KIPS (kilo instructions per second), which equals 0.001 MIPS. The first general purpose microprocessor, the Intel i8080 ran at 640 KIPS. The Intel i8086 microprocessor, the first 16 bit microprocessor in the line of processers made by Intel and used in IBM PC's, ran at 800 KIPS.

Early 32 bit PCs (386) ran at about 3 MIPS.

Year 2004 budget PCs, 32 bit(Celeron) are rated at about 10,000 MIPS, while 64 bit(Opteron) are about 8,000 MIPS.

zMIPS[1] refers to the MIPS measure used internally by IBM to rate its mainframe products (z-series).