abacus - a calculator that performs arithmetic functions by manually sliding counters on rods or in grooves

adder - a machine that adds numbers

adding machine, totaliser, totalizer - a calculator that performs simple arithmetic functions

tabulator, counter - a calculator that keeps a record of the number of times something happens

hand calculator, pocket calculator - a calculator small enough to hold in the hand or carry in a pocket

machine - any mechanical or electrical device that transmits or modifies energy to perform or assist in the performance of human tasks

Napier's bones, Napier's rods - a set of graduated rods formerly used to do multiplication and division by a method invented by John Napier

quipu - calculator consisting of a cord with attached cords; used by ancient Peruvians for calculating and keeping records

subtracter - a machine that subtracts numbers