If you have to ask then it is probably too early. You will know it is the right time when you don't have any doubts at all. If two people are in love a few more weeks or months won't make a difference.
Your questioning is a good indicator: it may be early. Key "tells" include going through a significant array of life experieinces and watching each other interact with both families.
If you are asking this question, it is too early to be engaged. You will automatically know when you want to get engaged, the feeling will be right, and you will not have to question it.
You should not get engaged to be married until you thoroughly know each other. Have you met his family - and like them? Is his credit reasonable? Does he have a criminal record? Does he have children that you don't know about?
