The standard way to measure your penis is with a rigid ruler, pressed against the pubic bone, while fully erect. This method, known as bone-pressed erect length, is the same one used in clinical research, which means it gives you a number you can accurately compare to published averages. Getting a consistent result takes a bit more care than you might expect, so here’s exactly how to do it.
How to Measure Length
You’ll need a straight, rigid ruler (not a tape measure) for length. Measure only when fully erect, since flaccid size varies dramatically with temperature, stress, and blood flow and doesn’t correlate reliably with erect size.
Place the ruler along the top of your penis, starting where the shaft meets your body at the pubic bone. Press the end of the ruler firmly into the pubic bone, pushing past any fat or pubic hair. Then measure in a straight line from that point to the very tip of the head. Measuring from the top (the side facing your abdomen) is the clinical standard. Measuring from the bottom or the side will give you a different, less reliable number.
Pressing into the pubic bone matters because the fat pad above the base of the penis can partially bury the shaft, making it look shorter than it structurally is. In some men, this fatty tissue hides a few centimeters of length. Pressing the ruler to the bone gives you the true skeletal measurement, which is the number researchers use and the only one that stays consistent regardless of body weight changes.
How to Measure Girth
For girth (circumference), use a flexible fabric tape measure or a piece of string you can mark and then hold against a ruler. Wrap it around the thickest part of the shaft while fully erect. Most men find the thickest point is roughly at the midshaft, but it can be closer to the base. Don’t pull the tape tight enough to compress the tissue. You want it snug against the skin, not squeezing.
Getting a Consistent Result
Penis size fluctuates throughout the day based on arousal level, hydration, salt intake, and even room temperature. Warmth causes blood vessels to widen, which means more blood stays in the penile tissue and creates a slightly fuller size. Cold does the opposite: blood is pulled toward the core, and the smooth muscle in the shaft contracts, drawing everything closer to the body. This is why a measurement taken after a hot shower can differ noticeably from one taken in a cold room.
To get a number you can trust, take three measurements over the course of a week. Measure at roughly the same time of day, in similar conditions (same room temperature, similar arousal level), and average the three results. A single measurement on a single day is a snapshot, not a reliable baseline.
How You Compare to Averages
A large meta-analysis published in BJU International, combining data from over 15,000 men, found that the average erect length is 13.12 cm (about 5.16 inches) and the average erect circumference is 11.66 cm (about 4.59 inches). These numbers come from measurements taken by clinicians, not self-reported, which matters because self-reported sizes tend to skew higher.
Most men fall within a range around those averages. If you’re anywhere in the neighborhood of those numbers, you’re statistically normal. The clinical threshold for micropenis in adults is a stretched length of about 7.5 cm (roughly 2.95 inches) or less, which is well below what most men measure. That diagnosis is rare and based on being more than 2.5 standard deviations below the mean.
Curved Penises
If your penis has a noticeable curve, measure along the top surface in a straight line from the pubic bone to the tip, not along the curve itself. Alternatively, you can use a flexible tape measure pressed gently along the top of the curve, then compare that to the straight-line distance. Clinical studies use the straight-line method, so that’s the number to use if you want to compare to published averages.
Why the Method Matters
The reason clinicians settled on bone-pressed measurement from the top is consistency. Measuring from the side, the bottom, or without pressing to the bone introduces variables that change from person to person and even from day to day in the same person. The fat pad above the pubic bone varies with weight, posture, and how recently you’ve eaten. Pressing to the bone eliminates that variable entirely. It also means that if you lose or gain weight, your measured length stays the same, reflecting the actual structural size rather than how much of it happens to be visible.
If your concern is visible length rather than structural length, you can take a second, non-pressed measurement for your own reference. Just know that the non-pressed number will be smaller and won’t match the averages reported in studies.