Sentencing Calculator API

Embed release date calculations in your application. Our public API allows external websites to calculate prison release dates under the Sentencing Act 2026.

Authentication

Public API

No API key required

Rate Limit

60 requests/minute

Per IP address

Format

JSON

Request & Response

Endpoints

POST https://insideoutjustice.com/api/v1/sentencing/calculate

Calculate an estimated release date. Send a POST request with sentence details in the request body.

GET https://insideoutjustice.com/api/v1/sentencing/regimes

List the active sentencing regimes (release fractions, eligibility, warnings) used by the calculator.

Request Body — POST /calculate

Parameter	Type	Required	Description
`startDate`	string	Yes	Sentence start date (YYYY-MM-DD)
`sentenceYears`	integer	Yes	Sentence length in years (0-99)
`sentenceMonths`	integer	No	Additional months (0-11), default: 0
`sentenceDays`	integer	No	Additional days (0-30), default: 0
`remandCreditDays`	integer	No	Days on remand to credit, default: 0
`taggedBailCreditDays`	integer	No	Tagged bail days to credit, default: 0
`addedDays`	integer	No	Added days from adjudications, default: 0
`sentenceType`	string	No	One of sds, sds_plus, section_250, eds, life, ipp, terrorism. Default: sds
`ageAtSentence`	string	No	One of adult, child, unknown. Default: adult
`regimeId`	string	No	Explicit regime ID (overrides sentenceType). See GET /regimes
`postCommencement`	boolean	No	Use the post-commencement (SA 2026) fraction. Default: false

Invalid input returns HTTP 422 with an errors object keyed by field name. Exceeding the rate limit returns HTTP 429.

Response — POST /calculate

Example Response (200 OK)

{
  "success": true,
  "data": {
    "releaseDate": "2027-09-08",
    "sentenceEndDate": "2030-03-01",
    "totalDays": 1461,
    "custodyDays": 584,
    "adjustedCustodyDays": 556,
    "fractionUsed": 0.4,
    "fractionLabel": "two-fifths (40%)",
    "warnings": []
  },
  "inputs": {
    "startDate": "2026-03-01",
    "sentenceYears": 4,
    "sentenceMonths": 0,
    "sentenceDays": 0,
    "remandCreditDays": 28,
    "taggedBailCreditDays": 0,
    "addedDays": 0,
    "regimeId": "sds_adult",
    "postCommencement": false
  },
  "disclaimer": "This is an estimate only and is not legal advice. Actual release dates are determined by HMPPS.",
  "poweredBy": "Inside Out Justice - insideoutjustice.com"
}

The data object always contains releaseDate, sentenceEndDate, totalDays, custodyDays, adjustedCustodyDays, fractionUsed, fractionLabel and warnings.

Response — GET /regimes

Example Response (200 OK)

{
  "success": true,
  "data": [
    {
      "regimeId": "sds_adult",
      "displayName": "Standard Determinate Sentence (Adult)",
      "description": "Fixed-term sentence with automatic release.",
      "fractionPreCommencement": 0.4,
      "fractionPostCommencement": 0.3333333333,
      "commencementDate": null,
      "eligibilityAge": "adult",
      "isExcluded": false,
      "exclusionReason": null,
      "warnings": ["Estimate only."],
      "sourceLinks": []
    }
  ]
}

Code Examples

JavaScript

// JavaScript/TypeScript
const response = await fetch('https://insideoutjustice.com/api/v1/sentencing/calculate', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Accept': 'application/json',
  },
  body: JSON.stringify({
    startDate: '2026-03-01',
    sentenceYears: 4,
    sentenceMonths: 0,
    sentenceDays: 0,
    remandCreditDays: 28,
    addedDays: 0,
    sentenceType: 'sds',
  }),
});

const result = await response.json();
console.log(result.data.releaseDate);

Python

# Python
import requests

response = requests.post(
    'https://insideoutjustice.com/api/v1/sentencing/calculate',
    headers={'Accept': 'application/json'},
    json={
        'startDate': '2026-03-01',
        'sentenceYears': 4,
        'sentenceMonths': 0,
        'sentenceDays': 0,
        'remandCreditDays': 28,
        'addedDays': 0,
        'sentenceType': 'sds',
    },
)

print(response.json()['data']['releaseDate'])

cURL

# cURL
curl -X POST 'https://insideoutjustice.com/api/v1/sentencing/calculate' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json' \
  -d '{
    "startDate": "2026-03-01",
    "sentenceYears": 4,
    "sentenceMonths": 0,
    "sentenceDays": 0,
    "remandCreditDays": 28,
    "addedDays": 0,
    "sentenceType": "sds"
  }'

Try It

Interactive API Tester

Start Date

Years

Months

Remand Days

Added Days

244ZA(7) Excluded

Terms of Use

Important Disclaimer

This API is provided for informational and educational purposes only. Results are estimates and should not be relied upon for legal advice.

By using this API, you agree to:

Display a disclaimer that results are estimates only
Link back to Inside Out Justice when displaying results
Not use the API for commercial purposes without permission
Respect the rate limits (60 requests per minute)

Required Attribution

When displaying results from this API, please include the following attribution:

Powered by Inside Out Justice Sentencing Calculator

Use Calculator View Guide GitHub