PDF Page Size Detector

How to use

1. 1Drop a .pdf file onto the upload area or click Choose file. Up to 500 MB is supported.
2. 2The tool reads the PDF in your browser, walks the page tree, and shows the dominant page size and a per-page table.
3. 3Check the Mixed sizes flag to see whether every page is the same size or the document mixes A4 with Letter, has a different cover sheet, or includes oversized inserts.
4. 4Read each page's dimensions in millimetres, inches, points, and CSS pixels at 96 DPI, with rotation and orientation called out for printing or layout.
5. 5Use Copy summary to grab a plain-text report, or Clear to load a different PDF.

About this tool

PDF Page Size Detector answers the everyday question 'What size is my PDF?' without sending the file to a server. Drop a .pdf and the tool reports the dominant page size (A4, US Letter, Legal, Tabloid, A3, A5, and many more), flags whether the document mixes page sizes, and lists every page with width and height in millimetres, inches, points, and CSS pixels at 96 DPI. The dimensions come straight from the PDF specification: each page is a dictionary with a /MediaBox entry whose array [llx lly urx ury] is expressed in user-space units (1/72 inch). When a page does not carry its own /MediaBox the value is inherited from an ancestor /Pages node, so the tool walks the /Parent chain up to the page-tree root to resolve the correct box. The /Rotate entry (an integer multiple of 90) is applied so the reported dimensions match what a viewer actually shows. Each set of dimensions is converted to millimetres and matched against a curated catalog of standard paper sizes: ISO A0 through A7, ISO B4 through B6, US Letter, US Legal, US Tabloid (Ledger), US Executive, US Statement (Half Letter), 4x6 / 5x7 / 8x10 photo prints, and DL, C5, C6, and #10 envelopes. Anything that does not match within about 1.5 mm of tolerance is labelled as a custom size and the raw measurements are kept visible. Mixed-size PDFs are detected by fingerprinting each page's rounded display dimensions, which is useful for spotting scanned inserts, oversized fold-outs, or pages someone forgot to crop. Everything runs locally with file.arrayBuffer() and an in-tab scan of the page tree, so the tool is safe for contracts, invoices, design proofs, print-shop submissions, scanned IDs, and any document you would rather not hand to a third-party service.

Free to use. Works in your browser. No signup, no login.