Soroban

Curio Vol 2 | Issue 6

Wooden beads slide through thin rods, clattering and clicking as they move up and down. The hands that move them are connected to a face usually engulfed in intense concentration and mental arithmetic. To the unlearned eye, it seems as if some form of mystic geometry is taking place. Perhaps this is true to some degree. Perhaps it is all a matter of putting counting into perspective.

This beaded instrument in reference is the Japanese tool known as the Soroban. Used to visualise mathematical sums, it is a type of abacus, and precursor to the modern calculator. Despite most abaci in other civilisations largely dying out, the Soroban is still widely used today in modern Japan.

The Soroban looks like a rectangular wooden frame, featuring an odd-numbered array of rods acoss its vertical axis. It is usually never less than nine, and often the standard number for these is thirteen.

On each of these rods are five total beads. Four of them are on the bottom section and one in the top section that sits above a horizontal beam called the ‘reckoning bar’. What is distinguishing about the reckoning bar is that it separates out the value of the top-bead and bottom-beads. (The top bead is five times the numerical value of a bottom-bead). In Japanese, this top-bead with a value of 5 is called the go-dama. Bottom beads with a value of 1 are called ichi-dama.

Despite its relatively simple architecture, Soroban are incredibly powerful tools that have enabled people to train their mental powers of mathematical addition, subtraction, division and multiplication.

Each of these four core operations requires a slightly different technique in utilising the Soroban; however the flexibility of the bead and rod setups allows for this to take place.


One of the key reasons why the Soroban is so effective is that it allows a visual representation of the decimal number system. The rods effectively resemble base-1o units (thousands, hundreds, tens, ones, tenths, etc.) and repeated use of Soroban allows a visual imprint when people are performing anzan — (blind calculation).

Man vs machine has always been an intriguing contest (for more, see Deep Blue, the computer program that played a chess match against Chess Grandmaster Garry Kasparov.) In a matchup between man and analogue technology vs man and digital technology; Kiyoshi Matsuzaki and his Soroban tested his arithmetic skill against Thomas Nathan Wood and an electric calculator in 1946. Scores were awarded on the speed and accuracy of results of five heats. The five heats corresponded to addition, subtraction, multiplication, division, and a heat where all four operations were combined. Matsuzaki and the Soroban won 4 to 1 (only losing in the multiplication heat).


Though much discipline and expertise is required to fully master the Soroban such that it can out-pace a calculator; expert users of Soroban swear that it changes the way in which humans process numbers and the way we do sums with the help of these beads. Skilled users can add 15 three-digit numbers in less than 10 seconds, which is a remarkable feat.

The Chinese Suanpan which was imported into Japan in the 14th Century, is the forefather to the Soroban. The key differences between these abaci is that the Suanpan has an additional bead on each rod (two top-beads and four bottom-beads) which allows for more complex calculations to be achieved. Arguably however, the methods for solving math operations are a little less elegant and streamlined than its successor.

Many variations of abaci span across different cultures and geographies, from Persia, Russia, Rome, Greece and Inca America. Most of these utilised pebbles or beads as their counting units, but differed in terms of the bases used for calculation. As mentioned previously however; many of these have died out, and the Soroban has endured in Japan.


The Soroban is an amazing invention; beguiling in its simplicity, and yet incredibly complex in the power of mental and visual arithmetic it can enable. While it doesn’t claim to be the most intuitive or easy-to-learn piece of technology to use; it is undoubtedly richly beautiful in its ability to visualise patterns, symmetry and improve mathematics in the mind.

Curio is released weekly on Mondays. Words and Illustrations by Rob Lee.