Generally speaking, if a penis measures less than three inches when erect it is classed as a micropenis.
Micropenisis are thought to be caused by insufficient levels of testosterone, but how does it feel to have one?
"Quite honestly, my entire life has been shaped and damaged by my penis size. I’m still not really over it, even though I’m way into middle age," a 51-year-old English teacher from the UK said in an interview with New York Magazine.
"I’ve had relationships, but they’ve never been terribly good, particularly not from my partner’s point of view. I always feel like I can’t do what I should be able to do as well as most people. That’s what I worry about. And doctors have never been any help."
The man went on to say that penetrative sex is difficult for him. His first sexual encounter was particularly "traumatic."
"We got to a certain point and she couldn’t hide how disappointed she was. She was quite annoyed and I don’t blame her at all - to this day, I don’t blame her," he said.
Someone else who knows just how much penis size can affect relationships with the opposite sex is star of Unhung Hero Patrick Moote.
The actor and comedian's ex-girlfriend rejected his proposal of marriage because his penis was too small, among other things.
Talking to HuffPost UK Lifestyle about whether society places too much importance on penis size, he said: “Yes we do. The way people talk about it makes it seem more important than it is. Porn also gives it a weight that it shouldn’t have – the size, how women react to it being so big.
“The first time I saw another man’s penis was on the internet and it was a completely unfair representation of what a standard penis actually looks like. It also gives a really skewed version of what being intimate is – the guy’s penis looks like a baby’s arm and the woman is screaming like she’s being murdered.”
Moote said self-acceptance is the best way for a man with a micropenis to improve their sex life.
"What I realised is the more you embrace the insecurities the less people are likely to be able to break down," he said.
"What I realised is it takes more energy and time to change things about yourself that you can’t than it does to accept them. I’m way better about my insecurities because I can try to accept them or try to change them.”