My Fascination With The Abacus

Basic Principles





Getting Started

In Japan, an unbelievable amount time and research has taken place in order to determine the most efficient way to use an abacus. This section contains the essentials on how to move the beads in order to achieve the fastest performance from your abacus.

The Basic principles listed here are based on the infamous book The Japanese Abacus Its use and Theory by Takashi Kojima.

This book is a must have for any budding abacus enthusiast, and played an important role in fuelling the interest in the Japanese Soroban in the west.

Moving Beads

It is best to sit at a desk or table, and lay the abacus flat. When sitting in a soft armchair resting the abacus on a cushion, gravity is not your friend.

Operate the abacus with your right index finger and thumb. The left hand can be used to hold the abacus steady, or to mark a position on a page of numbers. The other three fingers on the right hand should be curled out of the way so that they do not interfere with the beads. If you are using a soroban, reset the abacus by tilting it forward so that all the beads fall to the bottom, place it back on the table, then run your index finger under all the 5 unit beads to move them away from the bar. For some reason, this is extremely satisfying.

Diagram 1 below shows the abacus with a value of 0.

A soroban showing zero

Diagram 1. A Soroban, showing zero



The correct fingers are important in building up speed.

Use the index finger to:

Use the thumb to:

Values

A bead counts when it is pushed towards the bar. 1 unit beads count when they are pushed up, 5 unit beads count when they are pushed down. The diagram below shows a soroban that shows 123,456,789.

A soroban showing 123,456,789

Diagram 2. A Soroban, showing 123,456,789



In the diagram, the rod designated to be the units rod is the fourth rod from the right.

General Rules

There are six general rules described by Takashi Kojima:

  1. Move down a 5 unit bead and move up one or more 1 unit beads at the same time.
  2. First move down one or more 1 unit beads, and then move up a 5 unit bead.
  3. Move down a 5 unit bead, and then one or more 1 unit beads in quick succession.
  4. First move up one or more 1 unit beads, and then move up a 5 unit bead in quick succession.
  5. When adding, operate on the unit rod first, then operate on the tens rod if there is a carry.
  6. When subtracting, operate on the tens rod first, before operating on the unit rod.

Addition and subtraction are the building blocks to all other types of calculation.
The next two sections describe how.