Prisons and probation

Number of people in prison and how full prisons are

Prison population statistics are published every week by the Ministry of Justice. The data shows prison populations by gender, the populations of both prisons and immigration removal centres (where people are temporarily detained) and the number of people on home detention curfews (as some short-term prisoners are released early on electronic tags).

Figures for each local prison are published on a monthly basis in the same place.

The number of young people in custody is published separately.

The capacity of prisons – published alongside population figures – is estimated on the basis of prison-by-prison judgement, taking into account the need to maintain proper security. The national figure for all prisons is called ‘Usable Operational Capacity’ and is the sum of all local prisons’ capacity minus 2,000 (the so-called ‘operating margin’, which accounts for the occasional need to provide separate accommodation for certain prisoners).

Prison population figures by gender are published as far back as 1900. These annual averages are published in the offender management caseload statistics annual tables – another section of the Ministry of Justice website.

Detailed data on sentence lengths and prisoner characteristics since 1993 is published by the Ministry of Justice as part of the ‘Story of the prison population’.

International comparisons of the prison population are available from the House of Commons Library.

What prison sentences people can get

There are essentially three types of prison sentence: suspended, determinate and indeterminate

Suspended sentences don't actually involve going to prison, provided offenders comply with the requirements set by the sentence (such as obeying curfews or undertaking treatment for alcohol addiction). 

Indeterminate sentences – including life sentences – involve a judge setting a minimum term, after which an offender can be released by a parole board on licence. The only exception is a 'whole life order', which means an offender can never be released.

Determinate sentences are the most common form of sentence. At present, if someone is sentenced to less than a year in prison, they're released at the halfway point with no further obligations (although they could have to spend the sentence at a later date if they commit a further offence).

Data on the type and length of sentences given for different offences is published as part of Ministry of Justice criminal justice statistics, which are produced every three months. Breakdowns are available by age, sex, ethnicity, offence, type of court and average sentence length. Historical figures date back to 2002.

Detailed figures for the average sentence length given for each offence is provided in the more detailed annual tables, which are put out with the quarterly update to December each year.

Why people are in prison, who they are and how long they’re serving

Prison population statistics only provide summary snapshots of numbers. Figures for more detailed characteristics of the prison population are published separately as part of offender management caseload statistics and more specifically in prison population tables, which are released every three months.

The figures provide information on: the sentence lengths of prisoners and those in detention (including those on remand and how many are serving life sentences), minimum sentences, recalls to prison after being released, the type of offence prisoners committed, the ethnicity of offenders and the nationality of offenders (also available by individual prison). In all cases the data is broken down by age and sex.

These figures only provide top-level detail. More information on prisoners’ characteristics is published in the offender management caseload statistics annual tables. There is more specific data on: the offences that prisoners are serving sentences for, sentence lengths, prisoner ages, the religion of prisoners, and the number of previous convictions and cautions that prisoners have.

For most of these measures, trends over time are also published in the annual tables. These tend to date back to 2002.

Who’s being sent to prison and how long they actually serve

Figures for the prison population only look at everyone in prison at a given time, and don’t tell us very much about people who’ve been sent to prison lately. For these statistics, prison reception figures are available from the quarterly offender management caseload statistics, along with figures for those recalled for breaching a probation condition.

This data is broken down by age, sex, type and length of sentence, and type of offence. Further detail over time dating back to 2002 is available from the annual tables.

Prison discharge statistics are published in the same place, and can show not only how many people were released from prison in a given time period, but also the average length of sentence they ended up serving. Here is where we also find data on releases and recalls to prison on Home Detention Curfews (where some short-term prisoners are released early on electronic tags). Annual tables provide more detail and historical data back to 2002.

How well prisons are performing

HM Inspectorate of Prisons conducts routine checks and publishes reports on individual prisons and custody facilities across the country.

Prison performance can also be expressed numerically using key performance indicators such as: overcrowding, escapes (breaching physical barriers), absconds (no physical barriers) and positive mandatory drugs tests. These are published as part of the annual prison performance digest. Separately, prisons and probation trusts are rated for their overall performance between 1 (serious concern) and 4 (exceptional performance).

Figures for the number of offenders returned to custody and still at large are published separately as licence recalls in offender management caseload statistics.

Issues in custody

Some prisoners commit punishable offences while in custody. Figures for the number of offences (including violence, disobedience, wilful damage and unauthorised possessions) are published in offender management caseload statistics annual tables. The data is broken down by age, sex and ethnicity,

A wider series on safety in custody (including deaths, self-harm and assaults) is published annually by the Ministry of Justice. There’s also historical data, which for deaths in custody dates to 1978. The charity Inquest also has casework figures on deaths in prison and police custody.

Information on programmes undertaken by the prison service (including in the areas of domestic violence, sex offending, substance abuse and violence) is published as an accredited programmes annual bulletin.


There are three main types of probation supervision: community sentences, suspended sentences and youth rehabilitation orders (which are managed separately by Youth Offending Teams). The probation service also supervises people released from prison and those who are serving the final part of their sentence on licence.

Community sentences happen under ‘community orders’ and take place outside of prison, imposing requirements on offenders such as unpaid work or curfews.

Suspended sentences happen under ‘suspended sentence orders’ and are imposed when courts are minded to pass short prison sentences, but decide to hold off on prison provided the offender complies with restrictions similar to those for community sentences. If they don’t comply, they could be sent back to prison.

Youth Rehabilitation Orders are similar to community sentences in that they applying restrictions on children and young people. However, they can vary a lot in nature.

The number of people starting community suspended sentence or youth rehabilitation orders is published as part of the Ministry of Justice offender management caseload statistics put out every three months. The figures include details for the age and sex of the supervised, their offences, what type of restrictions they’re placed under, whether and why they’re terminated early, and breakdowns by local probation trusts. More details including historical data back to 2005 (when the sentences where introduced) are available from the annual tables.

The number of people recalled to prison for breaching probation conditions is published in recall statistics are part of the offender management caseload series.

Information on programmes undertaken by the prison service (including in the areas of domestic violence, sex offending, substance abuse and violence) is published as an accredited programmes annual bulletin.