Introduction
This Penis Size Calculator shows how your measurements compare to real research data. You type in your length and girth, and the tool tells you your percentile, your Z-score, and how rare your size is in a room of people.
You can measure in inches, centimeters, or millimeters. You can enter erect size, flaccid size, and flaccid stretched length. The tool also estimates volume for you, so you do not need to do any math.
All results come from published studies, like the Veale et al. review of up to 15,521 men.1 You can switch between studies, choose bone-pressed (BP) or non-bone-pressed (NBP) measuring, and skip studies with odd or clinical samples. A bell curve chart marks your spot in the population, and a step-by-step section shows every formula used.
There are also fun comparisons: everyday objects that match your size, how you line up with sizes women picked in a 2015 study, and the odds of being the biggest among a partner's past partners. Remember, these numbers are averages from small studies. Most men fall close to the middle, and size varies a lot from person to person.
How to use our Penis Size Calculator
Enter your measurements, pick a study to compare against, and the calculator shows your percentile, z-score, volume, rarity, and charts that mark where you land in the population.
Unit System: Pick inches/fl oz or cm/ml. Every box changes over right away.
Measurement State: Choose Erect, Flaccid, or All to set which of your numbers get scored.
Measurement Method: Pick BP if you pressed the ruler into the pubic bone, or NBP if you rested it on the skin. This choice decides which studies you can use.
Erect Length: Type your length from base to tip along the top of the shaft, or drag the slider.
Erect Girth: Type the distance around the thickest part of your erect shaft, measured with a tape.
Flaccid Stretched Length: Type the length when soft and gently pulled out.
Flaccid Length: Type the length when soft and relaxed at room temperature.
Flaccid Girth: Type the distance around the middle of the shaft while soft.
Volume Unit: Choose fl oz, ml, cm³, or in³ for all volume results.
Estimated Erect Volume and Flaccid Volume: These fill in on their own from your length and girth. You do not type them. The math is the same cylinder formula.
Your Height: Add your height to get a percentile compared to men your size. Leave the default if you would rather skip it.
Partner's estimated number of previous partners: Enter a number from 1 to 500. It is used only for the chance comparisons.
Study / dataset: Pick the research study used for the averages and percentiles.
Outlier studies: Include or exclude studies with a very wide spread (SD of 2.0 cm or more).
ED / clinical populations: Include or exclude studies of men in clinics for erectile problems or size worries.
Show scope: Show all studies, or just the recommended ones.
Room size preset and room size: Pick a crowd size, or type your own number, to see how many men in that group would measure at or above you.
Dimension to plot: Choose which measurement the bell curve chart shows. It is drawn from the same bell-shaped model.
Cell values and View mode: Set the comparison table to show averages, sample sizes, or volume data, and switch between a plain list or study sub-groups.
Calculate and Reset: Results update as you type. Click Calculate to refresh, or Reset to go back to the default values.
Penis Size: What the Research Says
Penis size is one of the most searched health topics, and most of what people hear is wrong. Real numbers come from studies where doctors, not the men themselves, did the measuring. The largest review, by Veale and others (2015), pooled clinician-measured data from up to 15,521 men and gave us the numbers most doctors use today.1
Average Penis Size
Here are the pooled averages from clinician-measured studies:
- Erect length: 13.12 cm1
- Erect girth: 11.66 cm1
- Flaccid length: 9.16 cm1
- Flaccid girth: 9.31 cm1
- Stretched length: 13.24 cm1
In inches those are roughly 5.2, 4.6, 3.6, 3.7 and 5.2. Most men land within about 2 cm of these numbers, and values much further out are uncommon.
How to Measure Correctly
Length: Lay a ruler along the top of the shaft and measure from the base to the tip. There are two ways to do this:
- BP (bone-pressed): Push the ruler in until it touches the pubic bone. This skips the fat pad and gives a longer number. Most medical studies use BP.
- NBP (non-bone-pressed): Rest the ruler on the skin. This reads noticeably shorter than BP.
Mixing the two is the biggest reason people think they are below average. Always compare BP to BP, and NBP to NBP.
Girth: Wrap a soft tape measure around the thickest part of the shaft. Girth is the circumference (the way around), not the width across.
Volume: This is an estimate, not a real measurement. The shaft is treated like a simple cylinder, so volume = girth² ÷ (4π) × length.
Why Self-Reported Numbers Run High
Studies where men measure themselves at home run higher: the Herbenick (2014) study of 1,661 men found a mean erect length of 14.15 cm, about a centimetre above the clinician-measured pooled figure.3 People round up, measure at the best angle, or use BP without saying so. That is why doctor-measured data is more trustworthy, and why sample size and confidence intervals matter when comparing studies.
What Percentiles Mean
A percentile tells you how you compare to other men. If your erect length is at the 60th percentile, you are longer than 60 out of 100 men. That is the same idea used in our Percentile Calculator. A z-score is the same idea in a different form: it counts how many standard deviations you sit from the average. A z-score of 0 is exactly average. About 68% of men fall between −1 and +1.
Things That Change the Numbers
Temperature, arousal level, time of day, body fat, and how recently you exercised all shift a measurement. Flaccid size changes the most and is a poor guide to erect size. Height is the only body measure with a consistent link, and it is weak to moderate: the review found correlations of 0.2 to 0.6 between height and stretched or erect length.1 This calculator's height adjustment uses 0.20, the low end of that range. Shoe size, hand size, and race are not reliable predictors.
Size and Partners
Research on what partners prefer, such as Prause and colleagues (2015), had 75 women choose among 3D models; they picked an average of 16.3 cm long and 12.7 cm around for a one-time partner and 16.0 cm by 12.2 cm for a long-term partner.2 These are averages from a small sample, and personal taste varies a lot. Surveys also show most women are happy with their partner's size, while many men are not. That gap is driven by comparison, not anatomy.
When to Talk to a Doctor
An adult stretched flaccid length far below the average is called micropenis, and it is rare. See a doctor if you notice a new curve, pain, shrinking, or trouble getting erections. If worry about size affects your daily life or relationships, that is worth talking about too. It is a common concern, and it can be treated.