Solitary confinement can last anywhere from a few days to years, but many prison systems treat 30 days or less as a typical disciplinary stay while others use it indefinitely. The UN’s Mandela Rules say anything over 15 days is prolonged and should not be used.

Typical ranges

  • A few days to 30 days : common for rule violations in some prisons.
  • More than 15 days : considered prolonged by the UN and widely viewed as harmful.
  • Months or years : happens in some systems through administrative segregation, supermax housing, or long-term isolation.

What makes it vary

The length depends on the prison’s rules, the reason for isolation, and whether it is punitive, administrative, protective, or part of pretrial detention. Some people are kept in isolation until staff decide they are no longer a risk, which can make the stay effectively open-ended.

Why it matters

Research and human-rights groups warn that prolonged isolation can cause serious mental-health harm, including anxiety, depression, paranoia, and self- harm risk. That is why many experts argue it should be used only in exceptional cases and for the shortest time possible.

Bottom line

So the practical answer is: solitary confinement is often measured in days or weeks, but it can stretch into months, years, or even longer in some prisons.