Online Abacus: Free Soroban and Chinese Suanpan

What an abacus teaches

An abacus is a place value chart you can move. Each rod is one place: ones on the right, then tens, hundreds and thousands going left. On each rod, beads above the beam (heaven beads) are worth 5 and beads below (earth beads) are worth 1. A bead counts only when it's pushed against the beam. So 1,947 is one bead on the thousands rod, a heaven bead and four earth beads on the hundreds rod, four earth beads on the tens rod, and a heaven bead and two earth beads on the ones rod.

This does two things for children learning arithmetic. It makes place value concrete: a bead on the tens rod is a ten, not a one. And the heaven bead groups numbers in fives, so 7 is seen as "5 and 2" rather than counted one by one, the same structure a rekenrek and ten frames build.

Soroban and suanpan: the two abacuses

The suanpan is the older of the two. It came to Japan from China after the mid-15th century, and Japanese users made it smaller and simpler, settling on one heaven bead and four earth beads, exactly enough for the digits 0 to 9. The suanpan's extra beads let one rod hold up to 15, which suited the traditional Chinese weight system (16 liang to a jin) and some older multiplication and division methods.

Switch between them on this board. The digits under each rod show when a suanpan rod is holding more than 9, and the readout explains how to carry the extra ten.

How to use an abacus

1. Clear it. Push every bead away from the beam. This abacus starts with the Clear button.
2. Find the ones rod. On this board it's the right-hand rod, labeled 1. (On a real soroban you pick a rod with a unit dot.)
3. Show each digit. For 7 on the ones rod, bring the heaven bead down (5) and push 2 earth beads up (2).
4. Read it back. Read the rods from left to right, like a written number.

Tap a bead to move it, and the beads between it and the beam move with it, just as your finger would push them on a real abacus. Tap a bead at the beam to push it away, along with the beads beyond it.

Adding and subtracting on an abacus

Abacus arithmetic works one place at a time, from the highest place down. For each place, there are three cases:

• There's room. Push up the beads you need. 2 + 2 on the ones rod: push up two more earth beads.
• Not enough earth beads: use the partners of 5. 3 + 4: there's only one earth bead left, so bring down the heaven bead (add 5) and take away one earth bead (subtract 1). 4 and 1 are partners of 5.
• The rod would pass 9: use the partners of 10. 6 + 7: add 1 on the tens rod (add 10) and take away 3 from the ones rod. 7 and 3 are partners of 10.

Subtraction reverses the moves. 12 − 5: the ones rod has only 2, so take 1 from the tens rod (subtract 10) and add 5 to the ones rod. That's borrowing, and on the abacus children see exactly where the borrowed ten goes.

Type a number under Guide me and press Add or Subtract to see these steps written out for your problem. For 47 + 25, the board lists two steps: first the tens rod ("not enough earth beads, so bring the heaven bead down and take away 3 earth beads"), then the ones rod ("no room for 5, so add 1 to the next rod and take away 5 here"). Next step makes each move, so the beads and the words stay together.

The abacus by grade

The Common Core standards don't require an abacus, but the skills it practices are named in them: understanding that the digits of a number represent amounts of tens and ones (1.NBT.B.2), composing and decomposing tens and hundreds when adding and subtracting (2.NBT.B.7), and knowing all sums of two one-digit numbers from memory by the end of 2nd grade (2.OA.B.2).

Activities to try

• Show your age, your house number, the year. Reading and setting real numbers builds fluency.
• Count by ones to 20. Watch what happens at 5 (the heaven bead comes down) and at 10 (a bead moves to the tens rod).
• Partners of 5 drill. Show 1, 2, 3 or 4 on the ones rod and add 4, 3, 2 or 1 the soroban way: heaven bead down, earth beads off.
• Count by tens. Add 10 again and again, using only the tens rod. When does the hundreds rod change?
• Suanpan puzzle. On the suanpan, show 10 using only the ones rod. (Both heaven beads.) Then carry it to the tens rod.
• Picture it. Close your eyes and picture the beads for 3 + 4. Experienced abacus users calculate this way, moving imagined beads.

Tips for teachers and parents

• Say the partners. "4 and 1 make 5; 7 and 3 make 10." The abacus method depends on knowing these pairs.
• Write as you go. After each step, write the new number. The What Works Clearinghouse practice guide on struggling students recommends linking concrete tools to written symbols.
• Go slowly at first. Accuracy before speed. NCTM's teaching practices favor building procedural fluency from conceptual understanding, which the guided steps make visible.
• Use the rekenrek first for young children. The rekenrek teaches the fives and tens without place value; the abacus adds place value on top.

What makes this online abacus different

Most online abacuses only let you click beads. This one moves beads the way fingers do, labels each rod's place value, shows each rod's digit and the expanded form, switches between a soroban and a suanpan, and guides addition and subtraction step by step with the partner numbers named. It adds undo and redo, share links, a printable snapshot, keyboard controls and ten self-checking task cards, and runs in any browser with no account.

For place value with blocks, try base ten blocks or place value disks. Families who like the abacus approach can compare programs in the best elementary math curriculum guide; RightStart Mathematics, for example, teaches its early lessons on an abacus grouped in fives and tens.