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 large Veale et al. review of over 15,000 men. 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. If you want to convert a single number by hand, the Cm to Inches Calculator and Inches to Cm Calculator handle that in one step.
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. If you only know the width across, the Diameter to Circumference Calculator converts it for you.
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. See the Volume Conversion Calculator if you need another unit.
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 used by our Cylinder Volume Calculator.
Your Height: Add your height to get a percentile compared to men your size. Leave the default if you would rather skip it. Curious where your height itself lands? Try the Height Percentile Calculator.
Partner's estimated number of previous partners: Enter a number from 1 to 500. It is used only for the chance comparisons, which follow the same rules as a basic Probability Calculator.
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). The Standard Deviation Calculator explains what that spread means.
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 behind our Normal Distribution Calculator.
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 data from over 15,000 men and gave us the numbers most doctors use today.
Average Penis Size
Here are the pooled averages from clinician-measured studies:
- Erect length: about 13.1 cm (5.2 in)
- Erect girth: about 11.7 cm (4.6 in)
- Flaccid length: about 9.2 cm (3.6 in)
- Flaccid girth: about 9.3 cm (3.7 in)
- Stretched length: about 13.2 cm (5.2 in)
Most men land within about 2 cm of these numbers. Sizes above 16 cm (6.3 in) erect or below 10 cm (4 in) erect are both 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 is usually 1–2 cm 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. If your ruler is marked in millimetres, the Mm to Inches Calculator keeps the units straight.
Girth: Wrap a soft tape measure around the thickest part of the shaft. Girth is the circumference (the way around), not the width across — the Circumference Calculator shows how the two relate.
Volume: This is an estimate, not a real measurement. The shaft is treated like a simple cylinder, so volume = girth² ÷ (4π) × length. Our general Volume Calculator uses the same approach for other shapes.
Why Self-Reported Numbers Run High
Studies where men measure themselves at home, like the Herbenick (2014) online survey, report averages more than a full centimetre larger than clinic studies. 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 — 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, and you can check any value with the Z Score Calculator. 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 and penis size are only weakly linked — the correlation is around 0.2, which is close to nothing, as you can test with a Correlation Coefficient Calculator. Shoe size, hand size, and race are not reliable predictors either. If you are tracking body composition alongside this, the Body Fat Calculator, BMI Calculator, and Waist to Height Ratio Calculator give a fuller picture than any single measurement.
Size and Partners
Research on what partners prefer, such as Prause and colleagues (2015), found women picked models averaging about 16 cm long and 12.7 cm around for a one-time partner, and slightly smaller for a long-term partner. These are averages from small samples, and personal taste varies a lot. Surveys also show most women are happy with their partner's size, while many men are not — a gap driven by comparison, not anatomy. For a lighthearted look at how stated preferences stack up against real distributions, see the Female Delusion Calculator.
When to Talk to a Doctor
A stretched flaccid length under 7.5 cm (about 3 in) in an adult is called micropenis and is rare, affecting roughly 0.6% of men. 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. For other men's health metrics, the Prostate Volume Calculator and PSA Density Calculator cover checks that become more relevant with age.