How to Measure Penis Size Correctly
The clinical bone-pressed method used in peer-reviewed research — so your measurement is actually comparable to the published averages.
Why measurement method matters: Different techniques can produce readings that vary by 1–2 cm for the same person. The only way to know where you actually fall on the population distribution is to use the same protocol the research used.
Step-by-Step: Length (Bone-Pressed)
Achieve a full erection
Measurements must be taken at full tumescence. Partial erection will understate your measurement. Take measurements while standing upright.
Position the ruler at the base
Place a rigid ruler on the top (dorsal) side of the penis, pressed firmly against the pubic bone. This is the bone-pressed (BPEL) standard. If you have a prominent fat pad, press through it until you feel the bone.
Measure from base to tip
Read the measurement at the tip of the glans (head). Do not include the foreskin if it extends beyond the glans. Round to the nearest millimetre.
Record in both units
Clinical research uses centimetres. Note your measurement in cm and convert: inches = cm ÷ 2.54.
Step-by-Step: Girth (Circumference)
Use a flexible tape measure
A cloth or plastic measuring tape works best. String and a ruler is an acceptable alternative — wrap the string, mark the overlap point, then lay it flat against a ruler.
Wrap at midshaft
The most common research reference point is midshaft — the halfway point between the base and the glans. Wrap snugly but not tightly.
Read the measurement
Where the tape completes the loop is your circumference. The population average from Veale et al. (2015) is 11.66 cm (4.59 in) at midshaft.
5 Common Measurement Mistakes
Most men who think they've measured themselves accurately have made at least one of these errors.
Always measure along the top (dorsal) from pubic bone to tip. Ventral measurement is longer due to penile curvature and not used in research.
Fat pad at the base obscures true length. Press the ruler firmly against the pubic bone to replicate the clinical standard.
Flaccid and erect measurements are not interchangeable. Only compare erect measurements to population erect averages.
Research varies — some studies use midshaft, some use base. Record where you measured. Midshaft is the most common reference point.
A rigid ruler held loosely at the base will give a shorter reading than bone-pressed. Press firmly.
BPEL vs NBPEL: Which Should You Use?
You'll see these acronyms in online discussions. Understanding the difference is important for valid comparison:
| Term | Full name | Used in research? |
|---|---|---|
| BPEL | Bone-pressed erect length | Yes — this is the standard |
| NBPEL | Non-bone-pressed erect length | Rarely — fat pad varies widely |
The published population averages (5.17 in erect length) are BPEL measurements. If you compare a NBPEL measurement to the published average, you will appear smaller than you actually are relative to the population.
Measurement Tools Compared
| Tool | Good for | Limitations |
|---|---|---|
| Rigid ruler | Accurate bone-pressed length | Can't measure girth |
| Flexible tape measure | Required for girth; can also do length | Slightly harder to hold against pubic bone solo |
| String + ruler | Works if no tape available for girth | More steps, slightly less accurate |
| AI image analysis | Hands-free, calibrated estimate, includes shape scoring | Requires good lighting and reference ruler in frame |
Quick Reference: What Your Measurement Means
| Erect length (BPEL) | Percentile |
|---|---|
| Under 10.5 cm / 4.1 in | Below 5th |
| 10.5 – 12.0 cm / 4.1 – 4.7 in | 5th – 25th |
| 12.0 – 14.2 cm / 4.7 – 5.6 in | 25th – 75th (middle half) |
| 13.12 cm / 5.17 in | 50th (median) |
| 14.2 – 16.0 cm / 5.6 – 6.3 in | 75th – 95th |
| Over 16.0 cm / 6.3 in | Above 95th |
Derived from Veale et al. (2015) nomograms. BPEL measurements only.
Sources
- Veale D, et al. (2015). Am I normal? A systematic review of penile measurements. BJU International, 115(6), 978–986. ↗
- Herbenick D, et al. (2014). Erect penile length and circumference dimensions of 1,661 sexually active men in the United States. Journal of Sexual Medicine, 11(1), 93–101. ↗