The Leibniz Step Reckoner and Curta Calculators
A Leibniz Stepped Reckoner calculator
In 1673, Leibniz built the first true four-function calculator. His unique, drum-shaped gears formed the basis of many successful calculator designs for the next 275 years, an unbroken record for a single underlying calculator mechanism. Leibniz built several versions of the Stepped Reckoner over about 45 years. Only one survives today.
The Leibniz Step Reckoner
Gottfried Leibniz’s 1673 “Step Reckoner” introduced a design innovation that enabled a single gear to represent any digit from 0 to 9 in just one revolution. This stepped-drum approach dominated calculator design for the next two centuries.
Gottfried Leibniz
Leibniz made many important contributions to mathematics, physics, logic, and philosophy, but he died in obscurity.
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Posthumous illustration of Stepped Reckoner mechanisms
For over 200 years, illustrators often depicted the Leibniz mechanism, which stimulated many subsequent inventors.
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Curta Calculator
The hand-cranked Curta was popular with sports car rallyists even after electronic calculators were available. The exquisite mechanism is still studied. There are several beautiful animations on the web, and a registry of current owners.
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While imprisoned in Buchenwald concentration camp in World War II, Curt Herzstark refined his pre-war design of a calculator featuring a modified version of Leibniz’s stepped drum. After the war, Herzstark’s Curta made history as the smallest all-mechanical, four-function calculator ever built.
Curta calculator parts, mid-1950s
A Curta calculator has more than 600 parts. The factory used special tools to build them, and an owner foolish enough to take one apart usually could not reassemble it.
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Curt Herzstark in Vienna
Herzstark worked in his family’s manufacturing business until he was sent by the Nazis to the Buchenwald concentration camp in 1943.
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