Measuring penis length and penis circumference

  • measuring the length of the erect penis: with a full erection with loosely applied ruler or folding metre stick from shaft to glans tip on the penis top side
  • curvatures are not taken into consideration
  • measuring the length of the flaccid penis: several measures at different times and occasions result in the average value
  • measurement of the penis circumference: with measuring tape applied loosely flush around the shaft of the erect penis
  • Penis circumference does not equal penis diameter

Measuring the length of the erect penis

The length of the erect penis is measured in fully erect condition. For this, a ruler or folding metre stick is held to the penis shaft starting at the belly and the distance up to the glans tip is measured (fig. 1). As opposed to the so-called "bone press" measurement, during which the ruler is applied with strong pressure, the loose application of the measuring instrument also takes into consideration the fat layer surrounding the penis shaft and, thus, determines the actually stimulatively useful length of the penis. Therefore, the measured result may differ depending on weight gain or weight loss

During the measurement it must be observed that the measuring scale of the ruler does not start with zero millimetres, but the number zero is somewhat displaced due to reasons of presentability. Therefore, mostly 3-5 millimetres of length can be added to the measured result. Example: If the measurement results in a penis length of 15.0 centimetres and the scale on the ruler starts after 5 millimetres, the penis is 15.5 centimetres long. 

A flexible measuring tape directly positioned on the top side of the penis may falsify the measured result when the penis is curved in an upwards direction (because a curve between two measuring points always results in a longer distance than a straight line). Therefore, in order that men are able to compare their penis lengths despite different shapes of their penis, the shortest distance between belly and penis tip must be measured at all times.

Note: The measurement of the length of the erect penis by stretching the flaccid penis manually implemented by urologists due to reasons of clinical practicability results in similar values, because the erect penis always can only be as long as in its stretched flaccid condition. However, in order to determine the length of the erect penis privately, the procedure described above must be preferred insofar as the actual physiological erection and, thus, the actually achievable size of the erect penis is measured with this method that may be significantly reduced in the event of erectile dysfunction (ED), for example.

Sketch of an erect penis with applied ruler for measuring the penis length
Fig. 1
Correct application of the ruler to determine the penis length.
alt="Sketch of an erect penis with wrapped measuring tape for measuring the penis circumference"
Fig. 2
Measuring the penis circumference (penis thickness)

Measuring the length of the flaccid penis

In its flaccid, non-erect condition, the penis has different lengths depending on the situation. Therefore, an average value must be determined by means of several measurements in order to measure the length of the flaccid penis (see also notes on the measurement above and the following example). 

Time of measurement
Measured value in cm
  • in the morning, after getting up
  • after lunch
  • in the evening before going to bed
  • after the sauna
  • after a cold shower
  • 10 minutes after an erection
  • after sports activities
  • Added values: measurements
    33,9 : 7
Average length of the flaccid penis:
= 4,8 cm

Determination of the penis type: Meat penis or blood penis

A so-called "meat penis" is insignificantly larger during an erection than in its flaccid condition. As opposed to this, a "blood penis" is significantly larger during an erection than in its flaccid condition. Men have a meat penis if the penis is a maximum of 1.9-times longer during an erection, i.e. just nearly doubles its length. If the penis length is more than double during an erection (over factor 2), it is a blood penis. 

Example meat penis (factor < 1.9):​

  • Penis length erect
  15,8 cm
  • Average penis length flaccid
: 9,9 cm
  • Factor:
= 1,6


Example blood penis (factor > 2.0):​

  • Penis length erect
  16,2 cm
  • Average penis length flaccid
: 5,1 cm
  • Factor:
= 3,2

Measuring the penis circumference on the erect penis

The penis circumference is measured on the fully erect penis. For this, a flexible measuring tape is positioned around the penis without strong tensile force, but flush, directly at the penis shaft. When talking about penis thickness, people commonly mean penis circumference.

Difference between penis circumference (penis thickness) and penis diameter

Frequently, the penis circumference is confused with the penis diameter. The penis circumference results from measuring the full circumference of the penis (fig. 1). On the contrary, the penis diameter is the imaginary shortest distance from one side of the penis to the other one. As it is not possible to position a ruler through the penis, the penis diameter can only be calculated: mathematically speaking, the penis circumference is the diameter divided by 3.14. If a man has a penis circumference of 12.0 centimetres, his penis diameter is 12.0 : 3.141 = 3.8 centimetres.