To measure penis length accurately, place a rigid ruler along the top of the penis, press the end firmly against the pubic bone, and read the measurement at the tip. This “bone-pressed” method is the standard used in clinical research because it accounts for the fat pad above the pubic bone, giving you a consistent number regardless of body weight. For girth, wrap a flexible measuring tape or a piece of string around the thickest part of the shaft.
How to Measure Length
You’ll need a rigid ruler or straight measuring tape. Measure while fully erect, since flaccid size varies widely based on temperature, stress, and arousal level. Stand upright or lean back slightly so the penis points straight out from your body.
Place the ruler flat along the top surface of the penis (the side facing up when you look down). Push the zero end of the ruler firmly into the pubic bone at the base, pressing through any fat or pubic hair. This is important: the fat pad above your pubic bone can hide a significant portion of length, especially at higher body weights. Pressing through it gives you what researchers call the “bone-pressed erect length,” which is the measurement used in virtually every major study on penis size. Read the ruler at the very tip of the glans.
If you don’t press to the bone, you’ll get a shorter number that fluctuates with weight gain or loss. That non-bone-pressed measurement isn’t wrong, but it’s less useful for comparison because it changes based on body composition rather than actual penile tissue.
How to Measure Girth
Girth is the circumference of the shaft. Use a soft, flexible measuring tape. If you don’t have one, wrap a piece of string around the shaft, mark where it overlaps, then lay the string flat against a ruler.
While fully erect, wrap the tape around the thickest part of the shaft. For most people, that’s somewhere around the middle, but the thickest point can also be near the base or just below the head. Keep the tape snug against the skin without compressing the tissue. Read the measurement where the tape overlaps itself. This single number is the most useful measurement for practical purposes like finding the right condom fit.
Getting a Consistent Reading
Several factors can throw off your measurement from one attempt to the next. Anxiety and adrenaline cause vasoconstriction, reducing blood flow to the penis and producing a smaller erection. Cold room temperatures have the same effect. Recent ejaculation can also make it harder to achieve a full erection. Most clinical measurements are taken at room temperature in a relaxed state, and you should aim for similar conditions.
Level of arousal matters more than people expect. A partial erection and a full erection can differ noticeably in both length and girth. If you’re measuring to get an accurate number, wait until you’re at peak arousal. Taking two or three measurements on different days and averaging them will give you the most reliable result.
What the Averages Actually Are
A 2023 systematic review in the World Journal of Men’s Health analyzed 75 studies covering 55,761 men. The pooled average erect length was 13.93 cm (about 5.5 inches). The average flaccid length was 8.70 cm (3.4 inches), and the average stretched flaccid length was 12.93 cm (5.1 inches). These are bone-pressed measurements, so if you measured without pressing to the bone, your number will naturally come in shorter than these averages.
Most men fall within a range, not at a single point. The 95% confidence interval for erect length in that review spanned roughly 13.2 to 14.7 cm, meaning the true population average sits somewhere in that window. Individual variation is wide, and being above or below the mean is completely normal.
Why Girth Matters for Condom Fit
If your reason for measuring is finding the right condom, girth is the number that matters most. Condom width (listed on packaging as “nominal width”) corresponds to your circumference, not your length. Most condoms are long enough for most people, but a condom that’s too tight or too loose around the shaft is more likely to break or slip off.
To figure out your width from your girth, divide your circumference by 3.14. That gives you the diameter, which you can compare against the nominal width listed on condom packaging. Condoms generally fall into three categories: snugger fit, regular fit, and larger fit. If a standard condom feels uncomfortably tight or rolls up during use, your girth measurement can point you toward the right category.
Common Mistakes to Avoid
- Measuring from the side or underside. The top of the penis, from the pubic bone to the tip, is the standard. Measuring along the underside follows the curve and typically adds length that studies don’t account for.
- Skipping the bone press. Without pressing to the pubic bone, your measurement is partially a reflection of your body fat percentage. If you want a number you can compare to published data, press firmly.
- Measuring while partially erect. Erection quality fluctuates. A measurement at 70% arousal and one at full arousal can differ by a centimeter or more.
- Using a curved or bent ruler. A rigid, straight ruler placed on top of the shaft is the most reliable tool for length. Flexible tape is better suited for girth.