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Sinclair Scientific &
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Inside Scientific

Sinclair Scientific

Displays only in scientific notation - 5 digit mantissa, 2 digit exponent, red LED (made by Bowmar).

4-function, limited scientific, reverse-Polish notation (RPN).

Main integrated circuit: Texas Instruments TMC0805 (here date coded to 1974, week 18).

6v (4 x AAA batteries).

50 x 111 x 19 mm (2.0 x 4.4 x 0.75 ins).

Made in England.

"Cambridge" series size, but not to be confused with the Cambridge Scientific.

Introduced in 1974, the initial price was 53.90 [about US$120] including Value Added Tax (VAT)[1].  Due to the reducing cost of components and intense competition the price soon dropped rapidly and the receipt for one example bought in July 1976 shows that it cost just 7 [about US$14] including VAT.

Click here to see an advertising brochure for the Sinclair Scientific (pdf format).

Great ingenuity was needed to shoehorn the program for scientific functions into the ROM of the TMS0805 chip, which was designed for use in basic four-function calculators.  More information about this achievement appears in the Sinclair Scientific page on the Vintage Calculators site.

Was also available as a build-it-yourself kit, as shown below.

Sinclair Scientific Kit

A Sinclair Scientific calculator kit, still shrink-wrapped in the polystyrene packaging.

Sinclair Scientific Kit
Sinclair Scientific Kit

The assembly instructions for the Sinclair Scientific calculator kit and the soft carrying pouch.

The components of the Sinclair Scientific calculator kit, there is also a bag of small parts out of view.

Clive Sinclair was very upbeat about the Sinclair Scientific calculator[2]:


"Our commanding lead in this technology enables me to predict that Sinclair will be the world's major manufacturer of scientific calculators", claimed Clive Sinclair, Managing Director of Sinclair Radionics at the company's first international sales conference held in London recently.
   Speaking to delegates from more than 40 countries, he estimated that by early 1975 20 per cent of all calculators will be purchased by professional scientists, engineers, architects, teachers and students.  In 1975 this will represent 3 million units throughout the world.  Purpose of the conference was to introduce the company's 49 pocket calculator, the "Sinclair Scientific" mentioned in March ETI.
   By the end of this year total calculator production on the entire Sinclair range will top 100,000 units per month.  The company is expected to introduce further additions to its calculator ranges over the next 9 months."

Giant Scientific

Giant scientific calculator

This amazing machine is a giant Sinclair Scientific calculator. It has the functionality of the hand-held model, but has the enormous size of 12" x 27" (30cms x 68cms).

Powered by 240v AC, it has a display formed of an array of dozens of discrete LEDs.

Grateful thanks go to Henry Padolsey for providing these incredible photographs.


This interesting photograph shows the array of discrete LEDs which make up the display, with the electronics boards below, all mounted on a substantial wooden back.

Display & circuit boards.

A close up showing the display LEDs and the electronics boards.


  1. "12-Function Scientific Pocket Calculator From Sinclair", Electronics Today International, March 1974, p6.
  2. "news digest", Electronics Today International, May 1974, p8.

Vintage British Calculators

Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.