Math practice · reimagined
Number bonds
Turn Number bonds into a fight you actually want to win. Every problem is an attack — solve it faster than your opponent and you land the hit.
Ages 4–99+ · no download · plays in your browser · 23 languages
How it works
Number bonds
Pick a fighter, choose Number bonds, and trust your numbers. The faster and cleaner you solve, the harder you hit — from gentle early grades all the way to Olympic-level challenges.
A number bond is two little parts that snap together to make a whole. Here the whole is 10 (and sometimes 20), one part is shown, and the other part is hiding behind the ?. Your job is to find the hidden part.
Picture 10 fingers. If 6 of them are up, how many are folded down? Four — because 6 and 4 together make 10. So 6 + ? = 10 means the ? is 4. You can count up from the part you can see until you reach the whole: from 6 it's 7, 8, 9, 10 — that's 4 steps.
Knowing the pairs that make 10 by heart (1 and 9, 2 and 8, 3 and 7, 4 and 6, 5 and 5) is a superpower — it makes every bigger sum easier later. Find the missing part and type it.
— Quick answers —
Number bonds: the short FAQ
- Is Number bonds free to play?
- Yes. Number bonds is free to play right in your browser — the whole curriculum, no download, no signup. Paid plans later unlock the full fighter roster, every stage and saved progress.
- Who is Number bonds for?
- Anyone from 4 to 99+. The early grades stay gentle for beginners, while the higher tiers will make even the confident sweat.
- Do I need to download anything to play Number bonds?
- Nope. Number bonds runs in any browser, on a laptop, tablet or phone.
- Can Number bonds be used in the classroom?
- Absolutely. Teachers run Number bonds with a whole class and track who's improving — see the schools plan for per-student pricing and a teacher dashboard.