Sunday, October 6, 2013

Erect penile length and circumference dimensions: a new internet survey - Need for a wider range of condom sizes

A new research study from the Indiana University research team was published online some time ago in the Journal of Sexual Medicine

Like many studies of penis size, they relied on men to report their penis size.
Then should we be concerned that men would lie about their size? No. Not really. 
Dr herbenick answers: 
"In fact, unlike most previous studies of self-reported penis size, they had good reason to report accurate data to us because we were using their size data to match them to a condom that was sized to fit their erect penis. If they reported a bigger-than-reality size to us, they would get a baggier condom. If they reported a smaller-than-reality size to us, the condom would be too tight."

  •  Measurement
It was performed using two erect penile measurement tools (one that used a letter-coding measurement system and a second that consisted of a centimeter-based measurement system) and detailed, illustrated directions about how to measure their erect penis, from the underside base and choosing the letter or numerical code that is “closest to the end of the head of your penis,” for the purposes of the study.

You will notice that the measurement is taken from the underside of the penis and therefore, can not be compared to the ususal measurement procedures.

  • Results
Below are the results obtained from this study and largely communicated to the media:
NB: values are in cm. Divide the value by 2.54 to get the equivalent in inches.

  • Discussion
I would like to spend some time about the concept of mean and standard deviation.
According to these raw results, one should expect that:
  1. 50% of men have an erect penis girth of less than 12.23cm.
  2. 84.13% of men have an erect penis girth of less than 14.46cm (mean + one standard deviation).
Provided that the data are normally distributed.
In fact this is absolutely not the case. Therefore, the standard deviation (2.23 cm) does not provide an accurate percentile rank. The real data give the following repartition:
  1. 50% of men have an erect penis girth of less than 12cm (this is obvious - the median was given).
  2. 84.13% of men have an erect penis girth of less than 13.5cm.
  3.  14.46cm would be at about the 93rd percentile!
The chart below give the detailed distribution:

  • Reminder
Normally distributed data looks like a bell curve. One has  to assume that penile dimensions data are not normally distributed because penile dimensions can not be smaller than a minimal value (in order to be physiologically functional), but the upper limit can be very high (before impacting negatively the functionality). 
The direct consequence is that the theoretical bell curve symmetry is broken with more individuals below the mean and grouped in a smaller range while fewer individuals are above the mean and distributed in a wider range.
When graphed, this type of data looks like a bell that leans to the left. 
In a effort to show it, I have gathered few "self-reported" studies, known to be "as serious as possible" scientifically. The collected data may not be as accurate as the one performed in a laboratory, but the phenomenon is more obvious as the number of tested individuals is important and therefore better reflects the broad range of penis sizes.
The selected studies are:
I have created a graph which compares these four studies to the few meaningful percentiles used when the curves are normally distributed:
  • the 50th percentile (the mean when it is normally distributed, the median otherwise)
  •  the 15.87th and 84.13rd percentile respectively representing the mean (M) - one standard deviation (SD) and the mean + one standard deviation when the distribution is normal
  • the 2.28th and 97.72nd percentile representing the M-2SD and M+2SD when the distribution is normal
  • the 99.87th percentile representing the M+3SD (the M-3SD was too small to mean anything) when the distribution is normal.
Graph: Cumulative percentile data of four erect penis circumference studies in cm compared to the usual normal standard deviations percentiles.

  • Conclusion
These data help showing once again the importance of having a wide choice of condom sizes, in order to better reflect the wide distribution of penis sizes.

According to the Herbenick study, as many as 15% of the male population has an erect penile girth of more than 13.5cm (5.3in). For this group, a normal sized condom is stretched 30%, which is really uncomfortable (for some, even painful) and accounts greatly for the high fail rate of condom usage.
The same can be said of the 15% of the male population whose erect penis girth is less than 10cm (4in). This group simply can not wear a normal condom without experiencing severe slippage.
Condom producers have a great responsibility in proposing the greatest possible range of condom sizes. Producers like Theyfit, My.Size or Coripa are more than welcome.

Sadly, sometimes, the governments are the cause of the lack of a wide choice. The best example is the US themselves which forbid the condoms to have an opening of more than 54mm (un-stretched circumference of 108mm). Let's hope this will change in the near future, thanks to people like Dr. Herbenick.

Debby Herbenick, Michael Reece, Vanessa Schick, Stephanie A. Sanders. Erect Penile Length and Circumference Dimensions of 1,661 Sexually Active Men in the United States.
The Journal of Sexual Medicine.

Other references:
Our New Research on the Penis Sizes of 1,661 American Men
Psychology today 
NB: To receive a copy of the full article from this penis size study, email Dr. Herbenick at cshp (at) indiana (dot) edu.
In the article you will be able to see some very interesting charts like:
  • Participant socio-demographic characteristics by penile length and circumference
  • Measurement and erection characteristics by penile length and circumference
  • Some discussion on the possible future research. 

Sunday, June 9, 2013

New penis survey from TheyFit: One size does NOT fit all!

Theyfit condoms reveal the largest, most accurate penis size survey data ever gathered.

You will most certainly be happy to discover how consistent these data are with the ones already gathered in this post, in this one, and in this one as well.

An anonymous sample of over 20,000 men shows that the UK ‘normal’ [size] is not 6 inches – it is nearly a whole inch less!
And whilst length is commonly the ‘measure of a man’, girth should not be overlooked as the survey reveals a staggering 4 inches difference when it comes to the circumference of the smallest and largest.

  • Average length is 5.1” (13cm), ranging from less than 3” up to more than 10”.
    • 26% of male population is less than 5" in Length,
    • 53% is between 5" and 6" in Length,
    • 21% is longer than 6" in Length.
  • Average circumference is 4.7” (12cm), with condom widths that fit girths of 3.5” up to 7.5”.

TheyFit’s size database was compiled by converting its unique "FitKit" measurements into metric sizes.
The FitKit provides each user with a randomised size code such as M17 or S77, so it’s not immediately obvious if someone needs a large or small condom.

Joe Nelson, founder of Theyfit comments, “Our anonymous data represent the most accurate survey of penis sizes ever collected. Previous studies have relied on self-reported measurements from men, leading to an issue of ‘size exaggeration’. But men buying our condoms are much less likely to do this for 2 reasons – firstly because they are parting with money for a custom fit condom and secondly because of our patented randomised size code system (rather than labels like small, medium and large), there’s simply less focus on whether someone is bigger or smaller – it’s all about getting a custom fit.”

I managed to get in touch with Joe Nelson himself, and he kindly answered to some of my further questions:

  • Was the circumference distribution normal (I believe you have less activity for standard sizes than for small or big sizes)?
Joe: Yes, quite a wide distribution. On the contrary, some of our happiest customers, based on feedback, are guys who have a nominal width requirement of 53 or 55mm, but love the fact that TheyFit are the correct length for them. Because we don’t market as “the condom for big or small guys” but instead as “the great condom for every guy” then I think this explains why guys of all sizes come to us, and enjoy us. Fact is, traditional condoms don’t fit nearly all guys, owing to being at least 7” long (but usually 205mm or 8.1”). 11 clinical studies dating back to 1993 identify fitting issues that 40-45% of guys experience, and they all think the number might be too low as many men don’t realise “it doesn’t fit” is even a valid complaint.

  • What is the standard deviation for circumference?
Joe: The s.d for nominal width was 6.4mm i.e 12.8mm circumference so almost exactly half an inch. We assume an average 18% latex stretch for optimum comfort, so you can expand it to circumference using that.

  • How did you build your data from numbers to cm (or in)?
Joe: [I] took a mid point for each letter/number. The critical part for accuracy is that the guys measuring are more likely to be honest. The midpoint methodology will cancel itself out over a large sample set like ours, from a mathematical perspective.

From all these information, we can draw some fair conclusions:
  • Average erect penis girth: 120mm +-15.1mm (4.7in +-0.59in)
  • Average erect penis length (do not press the pubic bone with your ruler): 130mm (5.1in).
  • About 10 to 20% condom stretch is tolerable for most guys (18% being the optimum for comfort with TheyFit comdoms), and above 25%, you are going to have a bad time. It's likely going to feel much too tight for you at the base.
  • Generally speaking, with store-bought condoms, above 135mm (5.3in) circumference you are going to be having issues with tightness and below 115mm (4.5in) a normal condom will likely be too loose and slip or fall off. 


TheyFit - Reddit FAQ

TheyFit - National condom day

The Inaugural TheyFit UK Size Study Survey