The MKS units is a metric system of units based on the meter, kilogram, and second. It was devised by A. Giorgi in 1901 and based on the earlier CGS units system.

In addition to the three basic units of length, mass, and time, the ampere was chosen as the unit of electric current and the value of the permeability of free space (μ₀) taken as 10^-7 henrys per meter (H m^–1). To simplify electromagnetic calculations, μ₀ was later changed to 4π × 10^–7 to give the rationalized MKSA system. This system, with some modifications, formed the basis of the SI system, now used internationally for scientific work.