How To Measure Penis Curvature
The best way to measure penis curvature is to use protractor or goniometer (kind of rulers to measure angles).
Most men do not measure the actual curvature… they estimate it.
Studies have shown that men with Peyronie's disease tend to overestimate their degree of penile curvature:
"A significantly higher proportion of patients overestimate their actual degree of penile curvature (54% overestimate, 26% underestimate, and 20% are accurate within 5 degrees, P = 0.002). Compared with objective measures, patients' estimates of degree of penile curvature differed by an average of 20 degrees ± 2.2 SE" (The Journal of Sexual Medicine, March 2009
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Measuring The Penis Curvature Yourself
You can measure the penile curvature yourself if you know how to use a Goniometer
The good thing about doing it yourself is that you can achieve the required erection in the privacy of your own home.
Have The Penis Curvature Measured By Health Professional
You can also have a health professional measuring your penile curvature. They can use photographs (AHP) you take at home of your erected penis or induce erection at the health clinic, with either vacuum erection pump (VED) or intracavernosal injection (ICI).
Studies have shown that ICI provides the most accurate penis curvature measurements.
"Our results show that the degree of curvature measured using vacuum-assisted device and AHP is underestimated as compared with the gold standard ICI" (The Journal of Sexual Medicine, January 2007
You need firm erection to accurately measure penis curvature. Erection achieved at home with the sole purpose of measuring or photographing the penis might not be as firm as "artificially" induced erection, i.e. by injection or VED.
While vacuum induced erection can appear straighter than normally, making them less reliable than ICI induced erection.
But does the exact degree of penile curvature really matter?
I guess the answer is both yes and no. Maybe what matters more is to measure penis curvature consistently, i.e. in order to evaluate if it is getting better or worse.
Consistent and accurate measurements are on the other hand very important if you are participating in a Peyronie's treatment trial, or if you are undergoing penile surgery.
Moreover, as we tend to overestimate the curvature... having the penis curvature accurately measured could make us feel a little bit better about our condition.