Altogether means completely, in total or on the whole.
- There were 50 people altogether.
- The plan was altogether unsuccessful.
- Altogether, it was a good experience.
All together means everyone or everything together in one place or at one time.
- The family sat all together.
- Let’s sing all together.
- Put the books all together.
Simple guide
Altogether = in total/completely.
All together = collectively or in one group.