Connections can happen in an instant, but forging deep friendships takes considerably longer—hundreds of hours, to be exact.

A new report published in the Journal of Social and Personal Relationships by University of Kansas professor Jeffrey Hall, found that it takes about 50 hours to turn an acquaintance into a "casual friend," and about 90 hours to become a good friend. Getting to BFF level, on the other hand, requires an average of 200 hours.

"We have to put that time in," Hall told Inc. "You can't snap your fingers and make a friend."

Hall came up with these estimates by surveying college freshman about how their friendships progressed. He found that college freshmen could quickly transition all the way to the close friend stage, which explains why we find it easier to forge strong friendships in our youth. "When people transition between stages, they'll double or triple the amount of time they spend with that other person in three weeks' time," Hall explained to Inc. "I found freshmen who spent one-third of all waking hours in a month with one good friend."

The study also found that hours that are not chosen—like the ones you spend with a coworker because you sit next to each other—have less of an impact. So in order to form a real friendship with a colleague, you'll need to spend time together outside of work, which means you should go ahead and put a happy hour on the calendar.

In the end, Hall can confirm that time spent on friendships is time well spent. "Maintaining close relationships is the most important work we do in our lives," Hall noted. "Most people on their deathbeds agree."