To measure your penis accurately, you need a rigid ruler for length and a flexible measuring tape (or a piece of string) for girth. The process takes about a minute, but small details in technique make a real difference in getting a consistent, reliable number. Here’s exactly how to do it.
How to Measure Length
Measure length while fully erect. Place a rigid ruler along the top of the shaft, with one end pressed gently into the skin where the penis meets your lower abdomen. Measure in a straight line from that base point to the tip of the head. Keep the ruler parallel to the floor, not angled upward or downward along a curve.
You’ll want to decide whether to press the ruler into the pubic fat pad or not, because the two methods give different numbers. Pressing the ruler firmly until it contacts the pubic bone gives you what’s called bone-pressed length (BPEL). This is the method most doctors and researchers use because it removes body fat as a variable. If your weight changes, a bone-pressed measurement still reflects the actual size of the organ itself.
If you don’t press into the fat pad, you get a non-bone-pressed measurement (NBPEL), which reflects visible length. This is the length a partner would see. Most people have roughly half an inch to a full inch of fat pad between the skin surface and the bone, though it can be significantly more at higher body weights. Someone with a bone-pressed length of 7 inches and a 1.5-inch fat pad, for instance, would measure 5.5 inches non-bone-pressed.
Both numbers are valid. Bone-pressed is more standardized for comparison purposes. Non-bone-pressed is more practical for things like condom sizing.
How to Measure Girth
Girth is the circumference of the shaft. Use a soft, flexible measuring tape and wrap it snugly around the thickest part of the shaft, which for most people is just below the head. Read the number where the tape meets itself. Don’t pull it tight enough to compress the tissue, but don’t leave slack either.
If you don’t have a measuring tape, wrap a piece of string or a thin strip of paper around the shaft instead. Pinch or mark the spot where it overlaps, then lay it flat against a ruler to get your circumference.
What If You Can’t Measure While Erect
If measuring erect isn’t practical, a stretched flaccid measurement is a reasonable substitute for length. Research published in The Journal of Urology found that stretched flaccid length closely predicts erect length, with a strong statistical correlation. To do this, gently stretch the flaccid penis to its maximum extension along the top of a ruler, measuring from the base to the tip. This won’t be perfectly identical to your erect length, but it’s the method urologists often use in clinical settings.
A regular flaccid measurement, without stretching, is not a reliable predictor of erect size. The same study found that neither age nor flaccid size accurately predicted how long the penis would be when erect. Some people are “growers” with a large difference between flaccid and erect size, while others are “showers” with relatively little change.
Common Mistakes That Skew Results
Measuring along the underside of the shaft instead of the top will give you a longer number because of the natural curve and the way the shaft connects to the scrotum. The standard is always along the top (the dorsal surface).
Angling the ruler is another common source of error. If you tilt it to follow an upward curve, you’re measuring arc length rather than straight-line length. Keep the ruler parallel to the ground and measure in a straight line even if your erection curves.
Temperature, stress, and arousal level all affect size, especially girth. Cold conditions and anxiety cause temporary constriction. For the most consistent result, measure at full arousal in a comfortable, warm environment. It’s also worth measuring on a few different days and averaging the results rather than relying on a single attempt.
How You Compare to Averages
A large meta-analysis published in the World Journal of Men’s Health, pooling data from studies across multiple countries, found the following averages:
- Erect length: 13.93 cm, or about 5.5 inches
- Stretched flaccid length: 12.93 cm, or about 5.1 inches
- Flaccid length: 8.70 cm, or about 3.4 inches
These are bone-pressed measurements. If you measured without pressing into the fat pad, your number will naturally be somewhat lower than these averages, so keep that in mind before comparing. Average erect girth across major studies falls in the range of 4.5 to 4.7 inches, though this varies by study population.
Most men fall within about an inch of these averages in either direction. The distribution is a fairly tight bell curve, meaning extreme sizes in either direction are statistically rare despite what online forums or pornography might suggest.
Why Consistent Technique Matters
If you’re measuring for condom fit, the numbers that matter most are your erect girth and your non-bone-pressed length. Condoms that are too tight restrict blood flow and increase breakage risk, while condoms that are too loose slip off. Many specialty condom brands now size by circumference, so having an accurate girth measurement lets you find a proper fit.
If you’re tracking changes over time, whether from weight loss, medical treatment, or any other reason, always use the same method each time. Bone-pressed length measured along the top of the shaft is the most reproducible approach because it eliminates the biggest variable: how much fat sits above the pubic bone on any given day.