It depends on the child

How old to be left alone?

I would say nine or 10 years old, but I think it also depends on the responsibility of the child. 

Some children are too wild and irresponsible to be left alone until they are much older.

It also depends on what time of day and for how long. 

I think 10 is OK after school for a few hours, but not to be left alone during meal times or into the evening and bed time or while sleeping.

Kevin Rossdahl