About this data
- Useable operational capacity is the total number of prisoners the prison estate can hold while maintaining good order and control, minus a margin kept free to manage the population (such as moving prisoners between prisons). It allows for cells to be shared beyond their uncrowded capacity.
- Uncrowded capacity (baseline certified normal accommodation) is the number of people prisons are designed to hold without crowding.
- Figures are snapshots from the Ministry of Justice's monthly bulletins (on the last Friday of the month) and, for October 2026, the latest weekly bulletin.
- In 2024, with prisons close to full, the government released many prisoners early: from September 2024, most standard sentences were released after 40% rather than half (SDS40). From October 2026, under the Sentencing Act 2026, most are released after one-third.
This chart appears in Prisons.