Of all the office tools that we’ve looked at in our History of Work series, the history of the calculator goes back the furthest. People have been looking for help with their sums since the development of mathematics, so you can draw a line from the current best-in-class tools for accountants right the way back to counting rocks and lines in the sand. 

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If we skip past the abacus, which kicks things off around 2700BC, the first office breakthrough came in the early 1600s, when the Scottish mathmatician John Napier invented logarithms. These enabled multiplication and division to be carried out in a way that could be mechanised, although his mechanism was very basic: Napier’s Bones were a series of square rods with multiplication tables carved on them which could be used for arithmetic calculation. The Halloween-style name was but the first in a series of creative titles that office technology is poorer for having abandoned. 

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Its first main successor was Pascal’s Calculator, created in 1642 to help with tax calculations in the French city of Rouen, and was followed by the Stepped Reckoner, developed in 1672 by Gottfried Liebniz. Both were highly effective tools, and neither achieved widespread adoption, chiefly because mechanical production wasn’t up to scratch. It would be another 200 years before the Industrial Revolution finally delivered reliable mechanisms - at which point both designs enjoyed success.

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The Stepped Reckoner had its moment thanks to Thomas De Colmar, who in 1820 devised the Arithmometer - another winning name. After many years of development it debuted at London’s World Exhibition before going on sale in 1851. A brass box with a series of levers, operated by turning a crank, it was simple to use and reliable enough to survive sustained office usage - it was so effective, it remained in production for almost 40 years, with various clones succeeding it.

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Pascal’s Calculator had a later renaissance. It wasn’t until later in the 1800s that a variety of inventors started producing key-driven accounting machines, which resembled a sort of Flintstones-esque version of the calculators we have today: a typewriter-style key for each number that engaged with a wheel mechanism that showed the numbers. The breakthrough was the Comptometer, invented by Dorr Felt in 1882, which combined this approach with Pascal’s mechanism and went into production in 1887. It was very successful and spawned a thriving industry across the world.

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The comptometer became much larger than previous mechanical calculators by having a column of ten keys for each digit in the number being calculated - one for the 1-10, then one for tens, hundreds, thousands and so on. This made comptometers a hefty desktop presence, but very fast in the hands of skilled operators, because each digit could be entered simultaneously. For this reason they stayed in use for a long time, only finally being retired in the 1990s. 

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Comptometers and arithmeters flourished for the first half of the 20th century, with steady improvements in mechanism design and manufacture making them smaller and more reliable - although they were still resolutely mechanical devices, powered first by hand cranks and then by electric motors, and almost as noisy as the typewriters they shared offices with. Miniaturisation gradually improved matters, with smaller and daintier “adding machines” becoming commonplace, and from the 1920s it was even possible to have a pocket calculator - still a mechanical device, commonly known as an Addiator, which came with a stylus to enter the numbers.

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Outside the office, meanwhile, two other approaches prevailed. One was the slide rule, chiefly although not exclusively used in engineering, which looked like an extendable ruler and was used to calculate multiplication and division along with more complicated tasks like trigonometry. The other was much simpler: the human “computer”, a person equipped with printed multiplication tables, who could work through tedious calculations in parallel with other “computers”. Both slide rules and “computers” arose in the 1600s and endured until well into the 1960s, with the human computers going on to work on the earliest mainframes that would inherit their title.

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The 1960s saw electronics come for the calculator, too, but slowly - early computers were big, complicated and very expensive, while calculators and adding machines were cheap office tools with a very price-sensitive customer base. Accordingly the ANITA Mark VII comptometer, launched in 1961, was powered by vacuum tubes, which kept it affordable while still claiming the title of the world’s first electronic calculator. 

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Electronics was advancing fast, though, and the decade wasn’t out before transistors and integrated circuit boards were cheap enough to create smaller, lightweight models. Electronic calculators went from heavy, mains-powered desktop machines to pocket devices very quickly, aided by the rapid growth of Japanese electronic firms like Sony, Sanyo and Canon. The first prototype portable calculator, which output on paper tape, was completed at Texas Instruments in 1967 - four years later, the Busicom Handy-LE was the first true pocket calculator, powered by batteries and with an LCD screen. 

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The 1970s saw an explosion in calculator production from a wide range of manufacturers, and prices rapidly dropped to the point where every business could use them. Older models endured in occasional niches (a hand-cranked pocket version of the Stepped Reckoner called the Curta, developed by an Austrian internee in a Nazi concentration camp, was used well into the 1980s by car rally racers, because it handled off-road driving much better than early electronics did) but the electronic calculator became the default for a short but glittering run from the 1980s through the end of the century.

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Unlike the other tools we’ve looked at in our History of Work series, its story has not ended there, even as the rise of desktop computing has transformed how businesses operate. The ease and simplicity of the desktop calculator means that it’s still being used in finance departments across the world - partially because for older users it’s second nature, but also because it’s routinely quicker to use a calculator and it doesn’t take up space on the computer screen. The oldest tool in this series has a sporting chance of being the most long-lived.

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The calculator’s persistence shows that the best solution for business is not always jumping to use the newest tool on the market, but taking the time to identify the bottlenecks and frustrations - and solving them is always easier if you can work with the tools that users are already familiar with. That’s the principle that guided the creation of Workiro, which was built to work with existing platforms like NetSuite and Office365, but solve the day-to-day operational problems that slow teams down. It’s beloved of accountancy professionals not because it helps with the sums - the simplicity of the calculator or its successor, the Excel formula, has that covered - but because it makes it effortless to track the documents, discussions and approvals that power the business. By connecting users, departments and clients, it enables you to access all the information for each project in a unified view within NetSuite. You can find out more by joining a group demo, or booking a one-on-one chat with one of our experts.