To measure your penis accurately, you need a ruler or flexible measuring tape, a full erection, and a warm room. There are two main measurements most people want: length and girth (circumference). Each has a specific technique that gives you a consistent, reliable number you can compare to clinical averages.
What You Need
A rigid ruler works for a straight penis. If yours has any curve to it, a flexible fabric measuring tape will follow the contour and give a more accurate reading. For girth, a measuring tape is essential. If you don’t have one, wrap a piece of string around the shaft, mark where it meets, then lay the string flat against a ruler.
Avoid stretchy tailor’s tape, which can give inflated numbers if you pull it tight. A standard fabric or paper tape measure is ideal.
How to Measure Length
Stand upright with a full erection. Hold your penis straight out from your body, parallel to the floor. Place the ruler or tape along the top of the shaft, starting from the base where the penis meets the abdomen. Measure to the tip of the head. This gives you what’s called the non-bone-pressed erect length, which reflects the visible length of the penis.
For the bone-pressed erect length, use the same position but press the end of the ruler firmly into the pubic bone at the base of the penis, compressing the fat pad. This accounts for the tissue that sits over the bone and gives a measurement closer to the full functional length, since during sex the fat pad compresses. The difference between these two numbers depends on body composition. Someone carrying more weight in the lower abdomen will see a bigger gap between the two. Losing body fat reduces the fat pad and increases visible length without changing the bone-pressed measurement.
Most clinical studies use the bone-pressed method, so if you want to compare your measurement to published averages, press into the pubic bone.
How to Measure Girth
With a full erection, wrap the measuring tape around the thickest part of the shaft, typically the mid-shaft. Keep the tape snug but not tight. Read the number where the tape overlaps itself. Some penises are thicker near the base or near the head, so you can measure at multiple points. The mid-shaft measurement is the standard one used in research.
Getting a Consistent Reading
Several factors can change your measurement from one session to the next. Temperature is the biggest variable. Cold causes blood vessels to constrict, reducing size. A warm room and full arousal give the most accurate baseline. During erection, increased blood flow actually raises penile skin temperature, which is part of why warmth and full arousal go hand in hand with maximum size.
Arousal level matters too. A 70% erection will measure noticeably shorter and thinner than a full one. Wait until you’re at peak firmness before taking a measurement. If you want a reliable number, measure on three different occasions and average the results. Day-to-day variation of a few millimeters is completely normal.
Stretched Flaccid Length
This measurement is used less often at home but is standard in clinical settings, particularly before implant surgery. To take it, press one hand flat against the area above the base of the penis to stabilize the fat pad. With the other hand, grip the head between your thumb and forefinger and gently extend the penis straight outward until it’s fully stretched but not uncomfortable. Measure from the base to the tip. Stretched flaccid length closely predicts erect length for most men and is useful if maintaining a full erection during measurement is difficult.
How Your Numbers Compare
A large meta-analysis published in The Journal of Urology pooled data from studies around the world and found the following averages:
- Erect length (bone-pressed): 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
Flaccid size varies dramatically based on temperature, stress, and recent physical activity, so it’s a poor indicator of erect size. Stretched flaccid length is a much better predictor. If your erect measurement falls within roughly an inch of 5.5 inches in either direction, you’re well within the normal range. Most men who think they’re below average are actually not, partly because the angles involved in looking down at your own body create a foreshortened view that pornography doesn’t.
Why Measurement Method Matters
If you’re measuring for condom sizing, visible (non-bone-pressed) length and mid-shaft girth are what matter. Condoms need to fit the part of the penis that’s exposed, and girth determines whether a standard, snug, or large condom will stay in place without being too tight or slipping off. Most condom size guides ask for your circumference in inches or millimeters. If you’re between 4.7 and 5.1 inches of girth, standard condoms typically fit well. Below that, look for snug fit options. Above 5.1 inches, larger sizes prevent the constriction that can reduce sensation or cause breakage.
If you’re tracking changes over time, whether from weight loss or any other reason, always use the same method (bone-pressed or not), the same tool, and similar conditions. Consistency in technique matters more than which technique you pick.