You may think you're pretty popular with more than 500 Facebook friends but don't kid yourself, says a new study. You still have only about five friends in real life.

Many of us have contact lists and followers on social media networks that extend into the thousands, but research conducted by Kiwi Dr Michael Harre suggests we could count our real friends on one hand.

The research, conducted at the University of Sydney, where Dr Harre is based, found humans have the capacity to let only a small number of people fully into their inner circle. That number could be as small as five.

Harre believes this upper limit has likely gone unchanged for hundreds of thousands of years and probably was how humans interacted when they lived as groups of hunters, in small groups.

"What our research showed for the first time is that complex layers of social groups are formed by adding one more person to our friends list," explained Dr Harre.

"And much like the ripples in a pond after you throw in a stone, the strength of each connection diminishes or weakens as they expand.

"Previously it was conjectured that our brains developed to the size they are to enable us to deal with the social complexity of other humans.

"Our findings show that maintaining about five links (friends), one for each social layer, is sufficient to support complex social networks of that size. It takes a lot of brain power to actually socially navigate these large networks and there's an upper limit to our ability to do that."

Dr Harre believes that when we add someone new to our social network, each new friend is slightly more distant than those in our inner circle.

It suggests that while we may have just a few friends, we can still surround ourselves with acquaintances.

Kiwi comedian Leigh Hart agrees, saying out of his 5000 friends on Facebook he knows just three.

"It makes sense, when you go travelling you only go with four or five people because any more than that causes chaos, everyone wants to go off and do different things," said Hart.

"I have five real friends, only just, more like seven actually."

Dr Harre, along with fellow researcher Dr Mikhail Prokopenko, explains that from an evolutionary perspective it was important to have small groups of close-knit social connections when humans were on hunting expeditions and other dangerous stations.

This would mean we do not have to be as close with the rest of the wider group, as long as we had a strong bond with around five others.