When humans counted on their fingers, everyone had a state-of-the-art (at the time) calculator at all times. But as we got smarter about calculation, we missed that convenience. When slide rules were king, techies were known to carry them around like swords swinging from their belts. These were replaced with electronic calculators, some also swinging from belt loops, but no matter how small they were, they still were not that handy, no pun intended. That changed around 1975. The Time Computer Calculator company produced an amazing calculator watch for Pulsar. At the time, Pulsar was a brand of the Hamilton Watch Company.
A Pulsar calculator watch (photo: The Smithsonian)
There were a few problems. First, the watch was thick. Despite its size, it had tiny keys, so you had to use a little stylus to push the keys — not as handy as you might wish. On top of that, 1975 display technology used power-hungry LEDs. So, the display was prone to turning off quickly, and the batteries died quickly.

Unsurprisingly, Hamilton, in conjunction with Electro/Data, had earlier rolled out the first LED watch in 1972. With an 18-karat gold case, it went for a cool $2,100 — a whole lot of money in 1972. The first calculator watch was also gold and went for almost $4,000. Soon, though, they brought out a stainless and a gold-filled version that came in at under $500.

Hewlett-Packard

The HP-01 (photo: [Stanlkocher] CC-BY-SA-3.0)Not to be outdone, HP created the HP-01 in 1977. These also came in gold and stainless models. Prices ranged from $450 to $850. You needed a special kit to do your own battery changes, so that added to the price, too. It also required a stylus. Unlike other HP calculators, the HP-01 did not use RPN.

For such a hefty price, these calculators didn’t do much. They were generally “four-bangers” with a few extra features, but they were no scientific calculators by any stretch of the imagination. The HP did have time and date calculations and could even use a stopwatch as a data source.

More calculator watches appeared directly from Time Computer Calculator Company and several others, but none were ever more than an expensive novelty. There were a few from companies like Seiko and Citizen. LCD screens would wipe out LEDs in watches, including calculator watches

Some lesser-known companies took their shots. Uranus Electronics was one. Hughes Aircraft also created an LED calculator watch with the name Compuchron.

Citizen had unusual round watches with tiny buttons around the circumference, including some that had scientific functions. These were the first calculator watches to use LCDs.

Seiko’s first entry had truly tiny buttons (see the video below). However, the C-515 had some of the nicest keys of the era, although design-wise, it was a bit blocky.

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The calculator from National Semiconductor had a flip-down keyboard cover. (photo: [Mister RF] CC-BY-SA-4.0)National Semiconductor produced a very powerful scientific calculator watch that was available under different names from different companies.

The National watch was a big hit in 1977 and a marvel of miniaturization. You can find some very detailed teardown pictures on Wikimedia Commons.

It is hard to say how many of these calculator watches were made and sold. Most are rare, and you would imagine the gold ones were not big production runs. Even the cheaper models seemed more like stunts than mass-market products.

Clearly, there was some demand, but things remained a niche market, and smaller players weeded out quickly. The calculator watch market was relatively sleepy until 1980 when Casio decided to make them.

Casio

The CFX-400 was a top-of-the-line scientific calculator that even did hex (photo: [Septagram] Public Domain)Casio made a large variety of cheap watches. The Casio C-60 appeared in 1980, the first of their calculators. It would set the basic design for many of their future models, like the popular CA-50 which, along with the similar CA-53W, appeared in movies like Back to the Future II and III.

The CA-50 was popular, and it appeared, along with the similar CA-53W, in popular movies, including Back to the Future II and III. These had tiny buttons, but you could carefully use them with your fingers. Some models had raised buttons. Others had flat buttons. A few even had a form of touch screen.

There were many variations in the Casio calculator watches. Some could store data like phone numbers and addresses. Others had scientific functions, like the excellent CFX-400 or the less-capable CFX-200. The CMD-40 even had a basic remote control.

The nicer models had metal cases, but many were plastic. There were even some that looked like a normal analog watch, but the top would flip up to reveal the calculator display and keyboard. Tricky to replace the batteries on those as you can see on the video below.

Calculator watches became something of a fad, especially with the pocket-protector crowd. However, like all things, they faded in popularity over time and now most are collector’s items.

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Today

You can find cheap calculator watches readily on the usual Chinese import sites. Casio still sells some vintage-series calculator watches, and there’s a brisk used market for the watches from any manufacturer. However, outside of the collectible value, most people switched to small calculators, PDAs, and — later — cell phones and smartwatches.

I owned several Casios, including a flip top and the FX-400. I also had the nice boxy Seiko. I don’t think they have made it unless they are hiding in a box somewhere waiting to be rediscovered. Which ones did you have? Do you have them now? Do you ever really use them?

Before you take me to task for not mentioning Sinclair’s wrist calculator, I will point out that it wasn’t really a watch. It was just a calculator that strapped to your wrist.

There have been DIY calculator watches, of course. It would be even easier to produce one today than ever before. It might be fun to grab one of the new ones and give it a brain upgrade. Let us know if you take up the challenge.

Featured image: “Casio Gold Calculator Watch” by [jonrawlinson].

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