It takes about 40-60 hours of time spent together in the first few weeks after meeting for people to form a casual friendship.

To transition from a casual friend to friend takes about 80-100 hours of together time.

For friends to become good or best friends, it takes about 200 or more hours spent together.

Different stages of a person’s life may require more or less time investment. Would a single young adult form friendships faster than a married middle-aged person? That’s a question Hall can’t answer with this study, he said.

Hours spent together strongly predicted friendship closeness, but not if that time was spent at work or in school — places where people weren’t interacting by choice.

The best way to spend time seemed to be just hanging out together, watching TV or playing video games together. People became closer by doing things they liked and enjoying each other’s company.

Time spent talking didn’t make people particularly closer, but chatting was better when they were striving to make a connection — catching up with their friends, asking them how their day was going and joking around. Small talk, on the other hand, seemed to be the enemy of friendship — people who talked about mundane topics become less close over time.