Why Prison and Jail Statistics Should Not Be Combined Casually

Prison counts and jail counts represent different correctional populations, often measured at different dates. The Bureau of Justice Statistics (BJS) maintains separate reporting series for these systems. Combining them without checking definitions can lead to misleading totals.

Here is the difference in plain terms. BJS defines a prison as a long-term facility run by a state or the federal government that typically holds people with sentences of more than one year. A jail is usually run by a county, city or other local law enforcement agency and holds people both before and after their cases are decided, including people serving sentences of a year or less. BJS counts the two in separate reports, on separate dates, using separate rules.

Two sourced numbers, side by side

• ✱Prisons: 1,254,200 people under the jurisdiction of state or federal correctional authorities at yearend 2023 (December 31, 2023). Source: BJS, Prisoners in 2023 – Statistical Tables, published September 2025.
• ✱Jails: 658,700 people held in the custody of local jails at midyear 2024 (the last weekday in June 2024). Source: BJS, Jail Inmates in 2024 – Statistical Tables, dated September 2026.
• ✱What the prison number measures: jurisdiction, meaning the legal authority of state or federal officials over a person, regardless of where that person is physically held.
• ✱What the jail number measures: custody, meaning people physically held in a local jail, regardless of conviction status or which agency has authority over them.
• ✱Reference dates: six months apart, in different calendar years.

Where the two counts overlap

Because one count is based on legal authority and the other on physical location, some people can show up in both. BJS's own reports show how:

• ✱At yearend 2023, 65,600 people under state or federal prison jurisdiction were housed in local jails, according to Prisoners in 2023.
• ✱At midyear 2024, local jails held 128,400 people for outside jurisdictions, including 55,600 for state prison authorities and 41,900 for federal authorities, according to Jail Inmates in 2024.
• ✱Six states (Alaska, Connecticut, Delaware, Hawaii, Rhode Island and Vermont) operate integrated systems that combine prisons and jails, and BJS counts everyone held in them as prisoners.

Simply adding 1,254,200 and 658,700 would therefore count some people twice, and it would blend two different dates. The overlap figures above also come from different dates, so they cannot be subtracted to produce a clean combined total. They show that overlap exists, not its exact size on any single day.

Other differences worth checking

• ✱Snapshot versus flow. Both headline figures are one-day counts. Jails also report admissions, 7.9 million from July 2023 through June 2024. An admissions count measures activity over a year and is a different kind of number from a one-day population, so the two should never be added together.
• ✱Conviction status. At midyear 2024, 68% of people in local jails (450,700) were unconvicted. By contrast, at yearend 2023, 96% of people under prison jurisdiction (1,210,300) were sentenced to more than one year.
• ✱Report timing. The newest national prison table in these BJS series describes yearend 2023, while the newest jail table describes midyear 2024.

None of these figures explains why populations rise or fall. They describe how many people were counted, where, and under whose authority.

What this means for families

• ✱When you see a large "total incarcerated" figure, check whether the source explains which dates it used and how it avoided double counting.
• ✱On Inmate Reviews, a county jail and a state prison serve different purposes. Use find a facility to check a facility's type before you compare facilities.
• ✱To find a specific person, use the official locator for the agency with authority over them: the county sheriff or jail for a jail, the state department of corrections for a state prison, or the Federal Bureau of Prisons for a federal prison.
• ✱Keep in mind that someone serving a state prison sentence may physically be housed in a county jail, so check both if a search comes up empty.