Skip To Content
Cambridge University Science Magazine
How much do you know about the development of the calculator? From rotary pinwheel calculators to hand-held stepped-drum calculators, the story surrounding these machines, conceptually simple yet mechanistically complex, deserves to be better known.

Today we see calculators as a useful feature on our phone. Yet when they were first invented, they were considered to be technological masterpieces, accomplishing calculations in a fraction of the time that would leave even the greatest mathematicians hunched over their desks for days.

The mathematician and philosopher Gottfried Leibniz developed the concept of stepped-drum calculators (also known as Leibniz’s wheel) as early as 1673.This involved a cranked system, which coupled a counting wheel with ten different sprockets and cogs of varying sizes to give an output in decimal representation. Invented in the 1870s by Baldwin and Odhner separately, the pinwheel mechanism built on Leibniz’s concept to further aid the development and capability of the mechanical calculator. Both the stepped-drum and pinwheel calculators performed multiplication and division by successive addition and subtraction, while the Millionaire calculator was the first direct multiplication machine in 1893.

One of the standout mechanical calculators was the Curta, often referred to as the “Math Grenade”, as it resembled the shape of a stereotypical hand grenade. This pocket-sized creation was the first portable calculator. It was developed by Curt Herzstark, an Austrian engineer, in the 1930s, and relied on Leibniz’s stepped drum mechanism. Curta calculators were widely considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.

So perhaps next time you reach for your phone to check a calculation, you will be reminded of the historical significance of their mechanical predecessors.

Kathryn Bowers is a BlueSci contributor.