We do not routinely measure the average length of stay of offenders in prison as to do so would mean examining a range of data including some offenders’ individual records. Therefore, to answer this question could only be done at disproportionate cost.
We do, however, prepare and publish the mean and median average time served by released prisoners in England & Wales according to sentence length. Some of this data can be found in the table below, a further breakdown is available in the attached tables.
Table - Mean and Median time served in prison by prisoners released from determinate sentences by sentence length and sex
Mean time (months) served by prison sentence (male and female prisoners)
Median time (months) served by prisons sentence (male and female prisoners)
(R) Existing data processing of average time served figures artificially rounded down to the nearest whole number of months. The revised figures presented here are based on unrounded average time served data. This change has had the effect of revising all of the previous time served figures and this has also resulted in a change in all of the 'percentage time served' figures.
(2) Due to improvements in IT systems, the 2015 prisons admissions data was taken from a different source, and, for statistical reporting purposes only, are produced using a different method.
The figures in these tables have been drawn from administrative IT systems which, as with any large scale recording system, are subject to possible errors with data entry and processing.