The Addiator was one of the predecessors of the modern calculator invented by Addiator Gesellschaft before the dawn of the computer era. These add/subtract calculators used purely mechanical parts for executing the operation of calculation. They featured a sturdy design made of sheet-metal sliders within a metal envelope. These calculators used an innovative design that utilized a carrying mechanism for calculation. They were manipulated with the aid of a stylus for operations such as addition and subtraction, made possible by flipping a front panel or by turning over the instrument.

The Addiator was a classic piece of equipment that made day-to-day calculations simple and cheap. Apart from standard calculations including addition and subtraction, it also enabled non-decimal measurements such as feet and inches, and even pounds, shillings, and pence. These machines were sold from the late 1920s till the early 1980s, and featured different 'screens' for different types of calculations. The latter versions incorporated extended sliders with an extra lower panel while the expensive sets included a built-in slide rule on the rear.

The early Addiator models were quite large; however, the latter versions were comparatively smaller and could fit in the pockets. These types of calculator were very popular during the 1970s, and also showcased in museums. The vintage models of the Addiator calculator can also be brought online, such as the vintage Arithma Addiator mechanical calculator with stylus, vintage Universal Addiator mechanical calculator and case, and antique mechanical Addiator calculator. The Addiator calculators are remarkable antiquities of history that offer a glimpse to the evolution of the present day calculators.