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PDF Page Size Detector

Measure every page box in a PDF and catch the mixed sizes that ruin a print run.

Processed locally in your browser. Your file is not uploaded to any server. How this works

  1. 01Add your file
  2. 02PDF Page Size Detector
  3. 03Download

Runs in your browser · nothing uploaded

About PDF page size detector

A PDF page does not have a size. It has up to five, and confusing them is why documents print at the wrong scale, come back from a bureau with the wrong margins, or arrive with one page of a hundred silently rotated. The MediaBox is the physical sheet the page is defined on. The CropBox is the region a viewer displays and a printer usually images, which is why a page can appear letter-sized while its MediaBox is larger. TrimBox is the finished size after cutting, BleedBox is the trim plus the margin of artwork that runs past the cut so no white sliver survives a misaligned guillotine, and ArtBox marks meaningful content for placement. This tool reports all of them, per page, in points, millimetres and inches, names the standard size where one matches, and flags mixed sizes and rotation — the two properties that most often explain a print result nobody expected.

How to PDF page size detector

  1. 01

    Load the PDF

    Every page node is read, with inherited box values resolved from parent nodes in the page tree.

  2. 02

    Check the size summary

    Pages are grouped by size so a document that is uniform shows one row, and a document that is not shows you exactly which pages differ.

  3. 03

    Compare the boxes

    Where CropBox differs from MediaBox, or TrimBox and BleedBox are present, each is listed so you can see the intended print geometry.

  4. 04

    Normalise if needed

    Use the page size changer for a uniform size, or the cropper to adjust the visible region.

What this tool does

  • MediaBox, CropBox, TrimBox, BleedBox and ArtBox per page, with inheritance from the page tree resolved
  • Dimensions in points, millimetres and inches, since print and office workflows speak different units
  • Standard size naming: A-series, Letter, Legal, Tabloid, and common photo and business-card sizes
  • Orientation per page, with the /Rotate entry applied so the reported size matches what a viewer shows
  • Mixed-size detection with a page-group summary rather than a hundred rows to scan
  • Bleed amount computed from the difference between BleedBox and TrimBox, in millimetres

Limitations worth knowing

Every PDF tool has constraints. Stating them plainly is more useful than discovering them halfway through your work.

  • Boxes are reported as the file declares them. A file can declare a TrimBox that does not match the artwork actually drawn on the page.
  • A missing TrimBox or BleedBox is not an error: most office documents have only a MediaBox, and readers fall back sensibly.
  • This measures; it does not resize. Changing page geometry is the page size and crop tools.
  • Content is not checked against the boxes, so this cannot tell you whether artwork actually extends into the bleed area.
  • Rotation is applied to the reported dimensions, which means the numbers here may differ from a tool that reports the raw MediaBox only.

How your file is handled

This tool runs entirely inside this browser tab. When you choose a file, your browser reads it from your own disk and hands the bytes to JavaScript running on this page — no network request carries your document anywhere. You can confirm that yourself: open your browser’s developer tools, switch to the Network panel, and run the tool. You will see no upload.

Nothing is stored after the fact. Closing or reloading this tab discards the file, the result and everything derived from them, because none of it ever left your machine. Read how local processing works.

Questions about PDF page size detector

What is the difference between MediaBox and CropBox?

MediaBox is the physical sheet the page is defined on and is the only required box. CropBox is the region a viewer displays and a printer typically images, and it defaults to the MediaBox when absent. When they differ, what you see on screen is smaller than the page really is — the extra area still exists in the file, which is why cropping in some tools hides content rather than deleting it.

Do I need TrimBox and BleedBox?

Only for commercial print. TrimBox is the finished size after cutting and BleedBox is that plus the overhang — typically three millimetres — where artwork runs past the cut so a slightly misaligned blade cannot leave a white edge. A print bureau reads these to impose and cut your job. For anything printed on an office printer or read on screen they are unnecessary.

Why did my PDF print at the wrong size?

Three common causes, all visible here. The pages are not the size you assumed, often Letter in a workflow expecting A4 or the reverse, which produces a small uniform scale error. The pages are not all the same size, so the printer scales to fit and different pages land differently. Or a CropBox smaller than the MediaBox means the printer is imaging a different region than you expect.

My document reports several page sizes. Is that a problem?

It depends where it is going. On screen it is harmless. For duplex printing or binding it is a real problem, because the printer will either scale pages inconsistently or shift them on the sheet. Merged documents are the usual source — combining an A4 report with Letter appendices produces exactly this. Normalise with the page size changer before printing.

Why does a page look like landscape but report portrait dimensions?

Because of the /Rotate entry, which tells a viewer to turn the page by ninety, a hundred and eighty or two hundred and seventy degrees at display time while the underlying box stays as authored. This report applies the rotation so the dimensions match what you see, and notes the rotation separately — which matters, because some print workflows honour it and some ignore it.

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