Mechanical Calculators

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Madas 20AZS

Madas 20AZG

Madas 20AZS

Mechanical, electrically driven, stepped-gear calculator.

4 functions - addition, subtraction, automatic multiplication, automatic division.

The accumulator is at the top and can show a result to 20 places of decimals. The numbers entered can be to 10 places of decimals.

375 mm x 320 mm x 215 mm (15" x 13" x 9"), 16 Kg (35 lbs).

Made in Switzerland by H.W. Egli S.A., Zurich.

Dates from mid-1950s (serial number 75173).

Underneath Madas 20AZS

View underneath, with the bottom cover removed, showing the electric motor which powers this model. Hand-operated models were also available.

The name 'Madas' is derived from the initial letters of "Multiplication, Automatic Division, Addition, & Subtraction". It is a mechanical calculator, driven by an electric motor and automatically performs the four standard functions (with a lot of whirring and clunking !).

These machines evolved over many years from the "Millionaire" calculator.


Further information:

Gerald Saudan has a site with information about everything that you would want to know about Madas mechanical calculators at, including details of all of the models.

Also, the history and internal workings of Madas calculators are described in an article by Ray Mackay at

In John Wolf's Web Museum there is an overview of Millionaire and Madas calculators, including pages showing a Madas calculator disassembled into its various mechanisms. It vividly illustrates the vast number of high-precision components required and the ingenuity in squeezing everything into a small space.

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2019  except where noted otherwise.