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Empire of the Sum: the Rise and Reign of the Pocket Calculator by Keith Houston

Rata I.’s Review for the 510 Club | March 2026

 

Keith Houston is a master of the microhistory, a genre that investigates broad historical trends through the focussed lens of a more esoteric subject. To date, he’s authored books about the development of punctuation, of emojis, of books themselves... and of pocket calculators. I’m in danger of typecasting myself, but how could I resist?

 

Unsurprisingly, Empire of the Sum’s narrative follows a similar structure to my recent calculator talk: this book, too, maps out a chronology from the earliest calculation aids to the modern era. Each of its 15 chapters is named for a specific device, one that the writer often eschews early on for unrelated (but no less fascinating) asides into concurrent mathematical, cultural and technological ideas, only to tie it all together again by the chapter’s end. Beginning with the human hand, then abacuses, slide rules, and early mechanical attempts, we get interesting tales of the people involved and the challenges they sought to solve. As with all human innovation, these histories are non-linear and studded with false starts and delectable ingenuity.

 

By the second half of the book we’re into the calculator business wars: the corporate competition of the electronics boom in the latter part of the 20th century. We see desktop mechanical devices replaced in short order by companies championing relays, transistors and microchips, which are in turn quickly usurped by the burgeoning computer age they create. Jointly comprising over 40% of global computational capacity in 1986 (measured in MIPS), calculators’ relative contribution drops to less than a thirtieth of one percent just 20 years later. The case is made that pocket calculators have hoisted their obsolescence by their own petard, now living on mostly as a “ghost in the machine.”

 

But this is a book dedicated to calculators’ moments in the sun. While weaving in wry comments on the eras (e.g. ”it was without irony that a member of the U.S. National Defence Research Committee could, in 1944, refer to a unit of computing power as a ‘kilogirl’”), goofy accounts of the human side of development (a vignette that made me laugh featured HP engineers sneaking in a carpenter to enlarge the space on holidaying boss Bill Hewlett’s desk, so that their new model would fit there as per spec), and lovingly descriptions of the machines in question, the underlying thesis is that as long as we are human, we will be always be figuring out ways to make maths work easier for us in some form or another.

 

Houston has been thorough in his research; the book’s chapters are backed up by about 50-100 references each (the last 82 pages of the book are dedicated to notes and further reading). The book is also well designed, with several colour images and diagrams, and each chapter heading illustrated with a neat evocation of its subject. Throughout, the writing style is charming, and doesn’t shy from clear technical explanations. Even I learnt a few things!

 

I summarily recommend this popular history of the calculator.

 

 

WHAT IS THE 510 CLUB?

The 510 Club is named after the Dewey Decimal classification for Mathematics. It is a book recommendation project facilitated by Mathateca in collaboration with Christchurch MathsJam. Each month we feature a mathematical book recommendation, whether that’s a novel, articles / essays, a puzzle book, textbook, biography... just as long as it features maths in some way. Read the above book at your leisure then feel free to comment your thoughts below, or come along to the following Christchurch MathsJam sessions to join in an informal maths/book chat with the reviewer.

We're always looking for suggestions! If you're interested in contributing a book rec one month, please email christchurch@mathsjam.com to sign up.