How many centimeters can a man take? We investigate after a case where penis size became evidence in court

In the Samara Region, a sexual assault trial ended with an unexpected verdict: the decisive factor in the forensic medical examination was the large size of the defendant's penis. The case sparked heated debate over whether there are strict anatomical limits to what the human body can accommodate during anal intercourse.

GBT Magazine Doberman.media examines, from medical and forensic perspectives, what actually determines the anus's ability to accommodate large sizes, why girth matters more than length, and why the absence of physical injuries does not necessarily mean that no assault occurred.

What happened in Samara?

By Messages According to media reports, a resident of the Samara Region filed a police report alleging that an acquaintance had broken into his apartment, threatened him with violence, and engaged in sexual acts without his consent. The defendant categorically denied breaking in and cited the unusually large size of his penis.

A court-ordered forensic medical examination measured the defendant's body and examined the victim, comparing the alleged mechanism of the act with the anatomy of both parties. The experts concluded that, given the stated dimensions of the organ and the circumstances described, penetration would inevitably have caused characteristic injuries, none of which were found on the victim. As a result, the rape charge against the man was dropped. However, the court found him guilty of making death threats and assault, sentencing him to 280 hours of community service and awarding compensation for emotional distress.

Is there a strict limit, measured in centimeters, beyond which the anus physically cannot accommodate an object?

Short answer: No, there is no universal numerical threshold in medicine.

Medical science has no rule stating that “penetration becomes physically impossible beyond 18 or 20 centimeters.” According to a major systematic review published in BJU International based on data from more than 15,000 men, the average erect penis is 13.12 cm long and has an average circumference of 11.66 cm. However, the anus's ability to accommodate larger objects depends on a combination of physiological and psychological factors, not simply a measurement on a ruler.

How is the anus structured, and why isn't it an "immovable tube"?

The anal canal is surrounded by a complex system of muscular sphincters. The internal anal sphincter consists of smooth muscle and functions reflexively, independently of conscious control. The external sphincter consists of striated muscle and can be controlled voluntarily.

If penetration is attempted improperly or too quickly, the muscles contract reflexively to protect the body. Moreover, the anal canal and rectum do not form a perfectly straight tube; they have natural curves and individual anatomical variations. For this reason, discomfort or tissue resistance may occur long before an object reaches any physical “limit.”

What matters more during penetration—length or girth?

From a mechanical standpoint, the greatest strain is caused specifically by the circumference (diameter), not the length.

Additional centimeters of length extend deeper into the rectum, which has sufficient capacity. Increasing the diameter, however, requires the sphincter tissue to stretch considerably around its entire circumference. In a 2023 study published in Journal of Sexual Medicine, researchers measured the peak mechanical force during anal penetration: the median was 26.5 N. Participants who regularly engaged in receptive anal sex required noticeably less force for penetration, confirming the muscles' ability to adapt.

Does the absence of injuries mean that penetration definitely did not occur?

No, it does not. And this is a crucial medical detail that is often omitted in simplified accounts of court cases.

• Meta-analysis data: A 2023 systematic review (3,165 participants) found that more than half of people who had experienced sexual violence had no detectable anogenital injuries.
• 2026 studies: An analysis of 306 cases involving medical attention following alleged violence in Berlin confirmed that visible injuries are found in only a minority of those examined.

Forensic medical experts emphasize that the absence of visible abrasions or tears cannot be interpreted as ruling out forcible contact. In the Samara case, however, the experts assessed a narrow and specific question: whether penetration could have occurred with the specific dimensions described, under the specific circumstances described by the victim without causing characteristic injuries.

Why can one person easily accommodate a large size while another experiences pain with an average size?

The ability to engage comfortably in receptive sex is determined by many variables:

1. Psychological comfort and freedom from anxiety: Fear, shame, and stress cause involuntary spasms of the sphincters and pelvic floor muscles.
2. Level of arousal: At high levels of arousal, the pelvic floor muscles relax naturally.
3. Quality and quantity of lubricant: Unlike the vagina, the anus does not have its own glands that produce natural lubrication.
4. Sexual experience and preparation: Regular, gradual dilation using anal trainers and dilators stretches the muscles without the risk of microtears.
5. Health conditions: Anal fissures, hemorrhoids, or pelvic floor hypertonicity can make penetration painful.

How can someone properly and safely prepare for larger sizes?

Sexologists and proctologists highlight several key safety rules:

• Use the right lubricant: The rectal mucosa consists of a single layer of epithelium that is sensitive to friction and osmolality. An isosmotic, water-based lubricant with a pH of 7.0–8.0 or a high-quality silicone lubricant is ideal.
• Avoid “numbing” gels containing anesthetics: Anesthetics mask pain—the body's primary warning sign of tissue damage—greatly increasing the risk of injury and tearing.
• Gradual dilation: The transition to larger sizes should be gradual, using fingers or a set of anal plugs of varying diameters.
• Speed control and deep breathing: A slow pace and deep breathing help consciously relax the pelvic floor muscles.

Key Takeaway

The Samara case clearly demonstrated how poorly informed the public is about the anatomy of anal contact. The human body has no fixed physical limit measured in centimeters beyond which penetration becomes impossible. With the right approach, a high level of arousal, and plenty of lubricant, the anus can accommodate significant sizes. However, in forensic science and medicine, one rule remains paramount: safety and voluntary consent come first, and the absence of physical signs of injury should never be treated as automatic proof that no violence occurred.