To measure your penis accurately, you need a rigid ruler or flexible measuring tape, a full erection, and a consistent technique. The method used in clinical research is called bone-pressed erect length, and it’s the standard because it accounts for differences in body composition and gives the most reproducible number. Here’s exactly how to do it, along with how to measure girth and what the numbers mean in context.
How to Measure Length
Start with a full erection. Partial arousal will give you a shorter, inconsistent measurement, and flaccid size varies too much with temperature and blood flow to be meaningful on its own.
Place a rigid ruler along the top (dorsal) surface of your penis, running from the base where the shaft meets your body out to the tip. Press the end of the ruler firmly against the pubic bone, pushing past any fat or hair at the base. Then read the measurement at the tip of the glans. This is the bone-pressed erect length, or BPEL, and it’s the number clinicians and researchers use because pressing to the bone removes the variable of how much fat sits over the pubic area. Two men with identical penile anatomy but different body weights would get different numbers without that firm press.
Measure along the top of the shaft, not the underside. The underside (ventral) surface runs a longer path because of how the anatomy curves at the base, so it inflates the number. A straight line from pubic bone to tip, along the top, is the standard.
How to Measure Girth
For circumference, use a flexible measuring tape or a strip of paper you can mark and then hold against a ruler. Wrap it around the shaft while fully erect, keeping the tape snug but not compressing the tissue.
European Association of Urology guidelines recommend recording girth at two locations: mid-shaft and just behind the head of the penis (the coronal sulcus). These two spots often differ, especially if the shaft tapers or flares. If you’re measuring for a practical reason like finding the right condom size, mid-shaft circumference is the most useful number since that’s where fit matters most.
Measuring with a Curve
If your penis has a noticeable curve, whether from Peyronie’s disease or natural anatomy, a rigid ruler in a straight line won’t capture the true functional length. In that case, use a flexible measuring tape laid along the top surface, following the curve from the pubic bone to the tip. This gives you the outer arc length, which better represents the actual tissue length.
For significant curvature, urologists typically measure stretched length from the skin junction at the base to the tip of the glans as a baseline. They may also measure the angle of curvature separately using a protractor-like tool during an induced erection. If you notice a new or worsening bend, that’s worth a clinical evaluation on its own, independent of length concerns.
Why Stretched Flaccid Length Isn’t a Reliable Shortcut
Some guides suggest stretching the flaccid penis and measuring from pubic bone to tip as a stand-in for erect length. Research from the Journal of Urology tested this directly in a group of men by comparing stretched flaccid length to actual erect length measured during an ultrasound-induced erection. The average stretched flaccid length was 10.8 cm compared to an average erect length of 11.8 cm, and 83% of men measured longer when erect. Nearly half had a discrepancy of 1 cm or more between the two measurements. The stretched method consistently underestimates, and in some men by a meaningful margin. If accuracy matters to you, measure while erect.
How Body Weight Affects Your Measurement
The penis is anchored to the pubic bone by internal ligaments, and a portion of the shaft extends behind the visible surface. When excess fat accumulates over the pubic area, it buries more of the shaft, making the visible portion shorter without any change to the actual anatomy. This is precisely why the bone-pressed technique exists. Pressing the ruler to the bone measures the full anatomical length regardless of body composition.
If you’ve gained weight and noticed a change in visible size, the underlying length is almost certainly the same. Weight loss can reverse the effect, making more of the shaft visible again.
Getting a Consistent Measurement
Several factors introduce variability if you’re not careful:
- Arousal level. You need a full erection, not 70% of one. Blood flow determines both length and girth, and partial arousal will undercount both. If you lose firmness during measuring, wait and try again.
- Temperature. Cold environments cause significant contraction of flaccid size, and even erect dimensions can vary slightly. Room temperature or warmer is ideal.
- Ruler position. Always measure from the top. The underside of the penis adds extra distance because of the angle where it connects to the scrotum.
- Pressing to the bone. If you skip this step, your number will vary depending on how firmly you hold the ruler, how much fat is present, and even your posture.
For the most reliable result, measure two or three times on different days and average the numbers. Single measurements can vary by a few millimeters depending on arousal quality and technique.
Average Size for Context
A meta-analysis published in the Journal of Urology pooled data from 75 studies spanning 1942 to 2021, covering 55,761 men worldwide. The averages were:
- Erect length: 13.93 cm (about 5.5 inches)
- Stretched flaccid length: 12.93 cm (about 5.1 inches)
- Flaccid length: 8.70 cm (about 3.4 inches)
These are means, which means roughly half of all men fall below these numbers and half above. The distribution follows a bell curve, so most men cluster relatively close to the average. Being a centimeter above or below puts you well within the normal range. Significant deviation from the mean, the kind urologists would consider clinically relevant, typically means falling more than two standard deviations below average, which in practical terms is quite rare.
When the Measurement Actually Matters
For most people, the reason to measure is either curiosity or a practical need like condom sizing. Standard condoms fit a mid-shaft circumference of roughly 11.5 to 13 cm (4.5 to 5.1 inches). If you measure outside that range, a snug-fit or large-fit condom will be more comfortable and more effective. Length matters less for condom selection since you can leave unrolled material at the base.
If you’re measuring because you’re concerned about size, keep in mind that the European Association of Urology’s 2023 guidelines specifically address penile size dysmorphophobia, noting that many men who seek clinical evaluation for short penile size fall within the normal range. Accurate measurement using the method above, compared against population data, gives you an objective reference point.