Each lower bead touching the beam adds 1 on its rod.
Learn by doing
See numbers on a real soroban
Move the beads, read numbers and solve exercises. No account, no public scores and no time pressure — one step at a time.
Interactive soroban
The upper bead is worth 5 and each lower bead is worth 1. Only beads moved toward the middle beam count.
How to read a soroban
You do not need every rule at once. Learn one rod first, then add the next place values.
The upper bead touching the beam is worth 5 on its rod.
From the right: ones, tens, hundreds, thousands and so on.
Set 3 on the tens rod and 7 = 5 + 2 on the ones rod.
First practice without the generator
Set 4. Move four lower beads toward the beam on the ones rod.
Set 5. Move the lower beads away and move the upper bead to the beam.
Set 8. Use the upper 5 and three lower beads: 5 + 3.
Set 12. One ten on the left and two ones on the right.
The key moves
How do addition and subtraction work?
Always try the simplest move first. When the simple move is impossible, use a complement to 5 or to 10.
5
Remember just two pairs that make 5
1 and 4 make 5. 2 and 3 also make 5. These pairs help you cross the upper bead.
1 + 4 = 52 + 3 = 5
If there is room, simply add
You have 2 and want to add 1. Move one more lower bead to the beam. You get 3.
2 + 1 = 3
First check whether you can do the operation with one simple move.
When there are not enough lower beads
Example: you have 4 and want to add 3. There are not three free lower beads.
- Add the upper bead: +5.
- That added 2 too much, so subtract 2.
- You are left with 7.
4 + 3 → +5 − 2 → 7
Why 2? Because 3 + 2 = 5. Three and two are complements to 5.
Example: 5 − 3
Only the upper bead worth 5 is active. There are no three lower beads to move away, so use an equivalent move.
- Move the upper bead away: −5.
- Move two lower beads in: +2.
- The soroban now shows 2.
5 − 3 → −5 + 2 → 2
We do not change the math. We replace −3 with −5 +2 because 3 and 2 make 5.
Example: 7 − 4
Seven is the upper 5 plus two lower beads. We want to subtract 4, but only two lower beads can be removed.
- Remove the upper 5.
- Give back 1 by moving one lower bead in.
- You get 3.
7 − 4 → −5 + 1 → 3
Why +1? Because 4 + 1 = 5.
Cheat sheet: moves around 5
When adding
+1 can be +5 −4
+2 can be +5 −3
+3 can be +5 −2
+4 can be +5 −1
When subtracting
−1 can be −5 +4
−2 can be −5 +3
−3 can be −5 +2
−4 can be −5 +1
Important: use a complement only when the direct move cannot be made. If you can simply add or remove the needed lower beads, do that.
10
Now learn the pairs that make 10
When the ones rod cannot handle the move, use the tens rod to its left. Remember the pairs that make 10.
1 + 9 = 102 + 8 = 103 + 7 = 104 + 6 = 105 + 5 = 10
Example: 8 + 5
Eight plus five will not fit on the ones rod. Move to the tens rod.
- Add one ten: +10.
- We added 5 too much, so subtract 5 on the ones rod.
- One ten and three ones remain: 13.
8 + 5 → +10 − 5 → 13
Instead of adding 5, add 10 and take 5 back.
Example: 9 + 4
The complement of 4 to 10 is 6.
- Add one ten: +10.
- Subtract 6 from the ones.
- The result is 13.
9 + 4 → +10 − 6 → 13
Four and six make ten: 4 + 6 = 10.
Example: 10 − 3
You have one ten and zero ones, so there are no three ones to remove.
- Remove one ten: −10.
- Add 7 on the ones rod.
- The soroban shows 7.
10 − 3 → −10 + 7 → 7
Why +7? Because 3 + 7 = 10. Remove the whole ten and give back the part you did not want to subtract.
Example: 13 − 7
There are only 3 ones, so 7 cannot be removed directly. The complement of 7 to 10 is 3.
- Remove one ten: −10.
- Add 3 to the ones.
- Three ones plus three ones gives 6.
13 − 7 → −10 + 3 → 6
Seven and three make ten: 7 + 3 = 10.
Cheat sheet: moves around 10
When adding past 9
+1 = +10 −9
+2 = +10 −8
+3 = +10 −7
+4 = +10 −6
+5 = +10 −5
+6 = +10 −4
+7 = +10 −3
+8 = +10 −2
+9 = +10 −1
When subtracting through a ten
−1 = −10 +9
−2 = −10 +8
−3 = −10 +7
−4 = −10 +6
−5 = −10 +5
−6 = −10 +4
−7 = −10 +3
−8 = −10 +2
−9 = −10 +1
Easy sentence to remember: when adding, “give 10 and take back the missing part.” When subtracting, “take 10 and give back the missing part.”
Try it slowly
5 − 3 = ?4 + 3 = ?7 − 4 = ?8 + 5 = ?9 + 4 = ?10 − 3 = ?13 − 7 = ?16 − 8 = ?
Set the first number on the abacus. Try a direct move first. If you get stuck at 5, use a complement to 5. If you need the next ten, use a complement to 10.
Back to the abacusExercise generator
Choose the exercise and number range. The score belongs only to the current browser session and is not sent to a server.
Choose an exercise and click “New task”.
You can use the abacus above.
Current abacus value: 0
Correct on first try: 0/0
Why learn with an abacus?
Place value becomes visible
Numbers are more than symbols. Each rod has a clear value that can be seen in the beads.
Counting is active
Instead of choosing a ready-made answer, the child performs the operation and can correct each step.
Child-friendly pace
There is no required timer and no punishment for mistakes. Hints explain the direction rather than finishing the task.
For parents and carers
Start with 0–9. Ask the child to say the move aloud: “the upper bead is five, I add two, so I have seven.” Move to tens only when one rod feels natural.
Read the parents’ guideFrequently asked questions
Do I need an account?
No. Exercises work without signing in. The session score is calculated in the browser.
What range should we start with?
Begin with 0–9, then 0–20. Understanding one rod and the upper bead is more important than speed.
What does the upper bead mean?
When it touches the beam, it adds 5 times the value of that rod: 5 on the ones rod, 50 on the tens rod, 500 on the hundreds rod.
Does the site save a child’s progress?
No. There is no child profile, public leaderboard or name form in this version.