The soroban (算盤, counting tray) is an abacus developed in Japan. It is derived from the Chinese suanpan, imported to Japan around 1600. Like the suanpan, the soroban is still used today, despite the proliferation of practical and affordable pocket electronic calculators.
The soroban is composed of an odd number of columns or rods, each having beads: one bead having a value of five, called go-dama (五玉, “five-bead”) and four beads each having a value of one, called ichi-dama (一玉, “one-bead”). Each set of beads of each rod is divided by a bar known as a reckoning bar. The number and size of beads in each rod make a standard-sized 13-rod soroban much less bulky than a standard-sized suanpan of similar expressive power.
The number of rods in a soroban is always odd and never less than nine. Basic models usually have thirteen rods, but the number of rods on practical models often increases to 21, 23, 27 or even 31, thus allowing calculation of more digits or representations of several different numbers at the same time. Each rod represents a digit, and a larger number of rods allows the representation of more digits, either in singular form or during operations.
The beads and rods are made of a variety of different materials. Most soroban made in Japan are made of wood and have wood, metal, rattan, or bamboo rods for the beads to slide on. The beads themselves are usually biconal (shaped like a double-cone). They are normally made of wood, although the beads of some soroban, especially those made outside Japan, can be marble, stone, or even plastic. The cost of a soroban can increase depending on the materials.
One unique feature that sets the soroban apart from its Chinese cousin is a dot marking every third rod in a soroban. These are unit rods and any one of them is designated to denote the last digit of the whole number part of the calculation answer. Any number that is represented on rods to the right of this designated rod is part of the decimal part of the answer, unless the number is part of a division or multiplication calculation. Unit rods to the left of the designated one also aid in place value by denoting the groups in the number (such as thousands, millions, etc.). Suanpan usually do not have this feature.
The Japanese Chamber of Commerce and Industry conducts examinations which soroban users can take to obtain licenses. There are six levels of mastery, starting from sixth-grade (very skilled) all the way up to first-grade (for those who have completely mastered the use of the soroban). Those obtaining at least a third-grade license are qualified to work in public corporations.
People who become proficient in use of soroban almost automatically become adept at mental calculation, known as anzan (暗算, “blind calculation”) in Japanese. As a part of soroban instruction, intermediate students are asked to do calculation mentally by visualizing the soroban (or any other abacus) and working out the problem without trying to figure out the answer beforehand. This is one reason why, despite the advent of handheld calculators, some parents send their children to private tutors to learn the soroban.
The soroban is also the basis for two kinds of abaci developed for use by blind people.