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The parts of a soroban
Five parts and one rule to remember: a bead only counts when it touches the beam.
Rods and the frame
A soroban is a wooden or plastic frame holding a row of vertical rods. Each rod holds one digit, so a board with thirteen rods can show a thirteen-digit number. Soroban usually have somewhere between 13 and 27 rods. More rods let you work with bigger numbers, or keep two numbers on the board at once, which is exactly what multiplication and division need.
The beam
A horizontal bar runs across every rod. This is the beam, sometimes called the reckoning bar. It splits each rod into an upper deck with one bead and a lower deck with four. The beam is the heart of the soroban: beads touching it count, beads away from it do not.
The heaven bead: worth 5
The single bead above the beam is the heaven bead. Pushed down to the beam it is worth 5. Pushed back up, it is worth nothing.
The earth beads: worth 1 each
The four beads below the beam are the earth beads. Each one pushed up to the beam is worth 1. Add the heaven bead and the earth beads together to read the rod.
Unit points
Look closely at the beam and you will see small dots on every third rod. These are unit points. Pick any dot to be your ones rod; the rod to its left is tens, the next is hundreds, and the dot three rods to the left marks thousands — just like the commas in a written number. Rods to the right of your ones rod are for decimals.
Clearing the board
Every calculation starts from a cleared board, with every rod showing 0. Tilt the soroban towards you so the earth beads slide down away from the beam, lay it flat again, then run your index finger along just above the beam to push every heaven bead up. Check each rod reads 0 before you begin.
Why one bead above and four below?
Four earth beads count 1 to 4. The heaven bead stands in for the fifth, so together they show every digit from 0 to 9 — the ten digits we write with, and exactly one pattern for each. Older designs with more beads could show 10 or more on a single rod, which the modern method never needs. Fewer beads means fewer choices, and fewer choices means faster, surer fingers.
Ready to try it?
Practise in “Meet the Board” →Common questions
What is the bar in the middle of an abacus called?
It is called the beam, or sometimes the reckoning bar. It divides each rod into an upper deck with one bead and a lower deck with four.
Why is the top bead on a soroban worth 5?
Because the four lower beads already cover 1 to 4. The top bead supplies the 5, so one rod can show every digit from 0 to 9 with exactly one bead pattern each.
What are the dots on a soroban for?
They are unit points, placed on every third rod. You choose one as your ones rod, and the others help you find thousands, millions or decimal places at a glance.