A free JSON endpoint with 23 paper sizes. No key, no sign up, no rate limit, CORS open to any origin. It is the same data behind the A4 versus Letter guide, which means it comes from ISO 216 and ANSI/ASME Y14.1 rather than from someone's spreadsheet.

Endpoints

GET /api/paper-sizes returns every size.
GET /api/paper-sizes/{code} returns one size, for example /api/paper-sizes/a4 or /api/paper-sizes/ansi-a. An unknown code returns 404 with a JSON error body.

Example response

GET https://printnook.co/api/paper-sizes/a4

{
  "code": "a4",
  "name": "A4",
  "series": "A",
  "standard": "ISO 216",
  "note": "The reference size for most of the world.",
  "mm": {
    "width": 210,
    "height": 297
  },
  "inches": {
    "width": 8.268,
    "height": 11.693
  },
  "cm": {
    "width": 21,
    "height": 29.7
  },
  "points": {
    "width": 595.28,
    "height": 841.89
  },
  "picas": {
    "width": 49.61,
    "height": 70.16
  },
  "pixels": {
    "96dpi": {
      "width": 794,
      "height": 1123
    },
    "300dpi": {
      "width": 2480,
      "height": 3508
    }
  },
  "aspectRatio": 1.4143,
  "areaCm2": 623.7
}

Codes

a0, a1, a2, a3, a4, a5, a6, a7, b0, b1, b2, b3, b4, b5, b6, b7, ansi-a, ansi-b, ansi-c, ansi-d, ansi-e, legal, executive.

Licence and attribution

The data is published under CC BY 4.0, which is also declared in an X-License response header. Use it in anything, including commercial work. The one thing asked in return is a credit: Paper size data from PrintNook with a link to https://printnook.co.

Stability

The endpoints are generated at build time and served as static files, so there is no server to go down and nothing to throttle. Fields will be added over time but existing field names and units will not change meaning. Millimetres stay the definitive value for the ISO series and inches stay definitive for the ANSI series, with every other unit derived from those.

Why this exists

Because getting paper dimensions right is a small, annoying, frequently botched job, and the numbers are already sitting here, checked, for the generators on this site. If it saves you retyping a table from Wikipedia, it has paid for itself. See how we measure for the conversions and the paper sizes guide for the same data as readable tables.

Paper sizes API