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calcu-pen sm wm

The year 1975 saw the introduction of a number of technological innovations. This list included such notable milestones as:

  • Rubik’s Cube was patented
  • Marcel Bich introduced his Bic disposable razor
  • Color television transmissions began in Australia
  • Microsoft was founded as a partnership between Bill Gates and Paul Allen
  • Sony introduced the Betamax videocassette recorder (VCR) for sale at $2,295.00 to the public
  • NASA rolled out the first space shuttle orbiter Enterprise (OV-101)

And while not quite the milestone of any of the above mentioned events, the year 1975 also saw the introduction of the Calcu-Pen in the United States.

Playground_Daily_News_Sun__Dec_14__1975 ad sm wm

newspaper ad from 1975

Made in Japan, the Calcu-Pen was a marvel of modern technology and design innovation marrying a ball point pen with an electronic calculator. The pen body was made of brushed aluminum while the calculator buttons and the power switch (located at the top of the pen) were made of plastic. The display was an eight digit LED. It is powered by an “N” size battery which is about the size of a half-height AA battery. The pen refill was laughably small at 0.875 of an inch long.

Overall the Calcu-Pen measures 6.25″ L and has a circumference of 2″. For comparison most modern pens measure about 1.5″ in circumference. It weighs two ounces but tends to be top heavy as the battery is located at the top of the pen.

The pen was advertised in the U.S. starting in 1975 through 1977. In 1975 it was sold for $79.95 but by late 1977 it was being advertised at $19.95. By 2015 standards $79.95 is a lot of money for a pen, but when you factor in inflation $79.95 in 1975 dollars equals $356.01 in 2015 dollars. This was modern electronics miniaturized to fit into a very high-quality pen and commanded an amount commensurate with its quality and advancements.

Playground_Daily_News_Thu__Jan_15__1976_ad sm wm

newspaper ad from 1976

As a pen it works well-enough but it is large and not well-balanced. This is unlikely to be your “go-to” regular use pen. The calculator portion was imaginatively designed using what was called quadraplane keys. You would actually press on one of the edges of the button to get the desired number or operation. The problem with these keys is that they were designed to fit into a small space but doing so made them difficult to operate. It was very easy to accidentally press the wrong edge. However, as long as you were careful it worked exactly as a calculator should.

The original U.S. patent for a calculator pen was filed in April 1975 and granted in February 1977 as patent number 4007364. Another patent showing the final manufactured design of the Calcu-Pen was filed in December 1975 and granted in June 1977 as patent number 4029915.

The primary inventor of the Calcu-Pen was a man by the name of Shin Ojima. I believe he worked for Hosiden Electronics in Japan. Like many inventors before him, Mr. Ojima had many ideas some of which you may not be aware of. Amongst his credits are such items as: the automatic bread baking machine (these things used to be sold everywhere), the analog electronic timepiece (an analog clock/watch where the hands and numbers are electronically generated on a screen), several electronic components, and a number of various pen calculators.

The manufacturer of the Calcu-Pen was never disclosed in any of the early advertisements. However, a company called Satolex which was formed by Hosiden Electronics was the credited manufacturer by 1977. I consider it very likely that Hosiden Electronics was the maker of the Calcu-Pen from the very beginning. An unsubstantiated source does credit Sharp with manufacturing the electronics for the pen but I cannot verify that. Hosiden is still in business today.

popular science october 1977 caclu pen ad only sm wm

magazine ad from 1977

Patent and Other Information:


  1. Smolowe, Jill (1977, January). Novelty Calculators. Popular Science, pages 58-59
  2. Hauman House (1977, October). advertisement. Popular Science, page 165
  3. Walls Bargain Center (1976, December). advertisement. Lawton Constitution, page 1d
  4. Cole, David J; Browning, Eve; Schroeder, Fred. Encyclopedia of Modern Everyday Inventions, Westport, CT, Greenwood Publishing Group (2003). Print
  5. Fred’s Showcase (1976, January). advertisement. Playground Daily News, page 17
  6. Editors, (©2015), Satolex. Retrieved March 29, 2015, from http://www.trademarkia.com
  7. Fred’s Showcase (1975, December). advertisement. Playground Daily News, page 4b