Our Methodology
We believe in transparency. Here's exactly how our tools work, where our data comes from, and what limitations you should be aware of.
Sentencing Calculator
How Release Dates Are Calculated
The mathematical basis for our estimates
Our calculator uses the release fractions defined in the Criminal Justice Act 2003 (as amended by the Sentencing Act 2026) to estimate automatic release dates:
- Standard Determinate Sentences (SDS): Release at ⅓ of sentence (post-April 2026)
- SDS+ (Section 244ZA): Release at ½ of sentence for certain serious offences
- Excluded sentences: Release at ⅔ of sentence for sex offences over 4 years
Date Arithmetic
We convert sentence lengths to days using the standard legal calendar:
Remand credit and added days are subtracted/added after the release fraction is applied.
Data Sources
Legislation
All legal references are sourced from legislation.gov.uk, the official home of UK legislation.
legislation.gov.ukOffence Lists
Schedule 15 offences are sourced from the Criminal Justice Act 2003 and updated when legislation changes.
Statistics
Prison statistics are sourced from the Ministry of Justice official publications and updated quarterly.
gov.uk/mojImportant Limitations
Our tools provide estimates only. They cannot account for:
- Individual circumstances that may affect release decisions
- Parole Board decisions for indeterminate sentences
- Complex sentencing scenarios (concurrent/consecutive sentences)
- Changes in behaviour affecting early release eligibility
- Future legislative changes
Always consult a qualified solicitor for advice specific to your situation.
Found an error?
If you believe any of our calculations or data are incorrect, please let us know.
View our Correction Policy →