See adding machine (disambiguation) for other uses of this term.

An adding machine was a class of mechanical calculator, usually specialized for bookkeeping calculations. In the United States, the earliest adding machines were usually built to read in dollars and cents. Adding machines were ubiquitous office equipment until they were phased out in favor of calculators in the 1970s and by personal computers beginning in about 1985. The older adding machines were rarely seen in American office settings by the year 2000.

Sumator to maszyna biurowa albo jej część wykonująca dwa, albo trzy podstawowe działania arytmetyczne: dodawanie, odejmowanie i mnożenie. Często utożsamiany z prostym urządzeniem liczącym zbudowanym z przesuwnych listewek.

Uma máquina de somar é um tipo de calculadora especializada, utilizada outrora para cálculos em contabilidade. Estas velhas máquinas podiam ser de manutenção difícil e davam respostas erradas caso o mecanismo falhasse. Provavelmente, era melhor aprender a usar um ábaco.