Rohman
A print shop asks whether your file is A4 or Letter. A submission portal rejects a PDF for being "the wrong size". A printer leaves a white strip along the bottom of one page and not the others. All three come back to the same question, and checking the PDF page size takes about ten seconds once you know where the number lives and what unit it's in.
Quick answer: To check PDF page size, open Page Size Inspector and drop in the file. It lists every page's width and height in points, inches, millimetres or centimetres, flags standard sizes like A4, Letter and Legal, and shows when pages differ. A4 is 595 × 842 points; US Letter is 612 × 792. Nothing is uploaded.
Why PDF Sizes Are in Points
PDF measures everything in points, and a point is exactly 1/72 inch. The PDF specification (ISO 32000-1, section 8.3.2.3) calls 1/72 inch the default unit of user space and notes it's "approximately the same as a point, a unit used in the printing industry."
So the conversions are fixed:
- 1 inch = 72 points
- 1 mm = 72 ÷ 25.4 ≈ 2.835 points
That's why A4, which ISO defines in millimetres, comes out as an awkward 595.28 × 841.89 points, while US Letter, defined in inches, lands on a clean 612 × 792.
PDF Page Size Chart: A4, Letter, Legal, A3, Tabloid
These are the sizes you'll meet most. A-series sizes come from ISO 216; Letter, Legal and Tabloid are the North American sizes (Letter and Tabloid also appear as sizes A and B in ASME Y14.1).
| Size | Points (pt) | Inches (in) | Millimetres (mm) |
|---|---|---|---|
| A5 | 419.53 × 595.28 | 5.83 × 8.27 | 148 × 210 |
| A4 | 595.28 × 841.89 | 8.27 × 11.69 | 210 × 297 |
| A3 | 841.89 × 1190.55 | 11.69 × 16.54 | 297 × 420 |
| Letter | 612 × 792 | 8.5 × 11 | 215.9 × 279.4 |
| Legal | 612 × 1008 | 8.5 × 14 | 215.9 × 355.6 |
| Tabloid | 792 × 1224 | 11 × 17 | 279.4 × 431.8 |
Sizes are written portrait, width first. A landscape page simply swaps the two numbers. Note how close A4 and Letter are: A4 is about 6 mm narrower and 18 mm taller. That's close enough to look identical on screen and different enough to clip a footer or leave a gap when printed.
How to Check PDF Page Size for Every Page
- Open Page Size Inspector and drop in your PDF.
- Read the overview. It groups pages by size, for example "4 sizes across 5 pages", and gives each group its paper name, orientation and page count.
- Switch units with the selector: points, inches, millimetres (the default) or centimetres.
- Check the per-page table below it. Consecutive pages of the same size collapse into one row, such as pages 1–2, so an odd page out stands out.
- Optionally, click Download JSON report to save every page's size, orientation and paper name.
When I ran a five-page test file through it, made with two A4 pages, one Letter page, one landscape A4 page and one odd 500 × 700 point page, it reported exactly that: A4 portrait at 210 × 297 mm, Letter at 215.9 × 279.4 mm, A4 landscape at 297 × 210 mm, and the last page as "Non-standard" at 176.39 × 246.94 mm.
The inspector names six sizes: A3, A4, A5, Letter, Legal and Tabloid, in either orientation, allowing 5 points of slack for rounding. Anything else is labelled Non-standard with its exact measurements, which is your cue to compare against the chart above.
Checking It Without a Tool
Adobe Acrobat and Reader will tell you the size of the page you're looking at: open File, then Properties, and the Description tab shows Page Size for the current page. Most other desktop readers have a similar properties panel.
That's fine for a single-size file. It's tedious for a 200-page document assembled from three sources, where the one Letter page in an A4 report is exactly what you're hunting for, because you'd have to visit every page. That's the case the inspector was built for.
Mixed Sizes, Odd Sizes and What to Do Next
Once you know the sizes, the fix depends on what's wrong.
Mixed sizes in one file. Merged documents often carry a scanned page or two at a different size. Fix Page Size brings every page to one target size, such as A4 or Letter, and lets you choose whether content is scaled to fit or cropped to fill. Page Size Inspector links straight to it through its Normalize sizes button.
Extra margin or a scanner border. If the page is the right shape but carries a white border, trim it with Crop PDF. Our guide to cropping PDFs explains why some croppers only hide content.
A page far too big. Large-format drawings and stitched pages can exceed 200 inches on a side, which Acrobat won't display in full. Our sibling guide to a PDF page that's too large covers that limit and how to split such a page.
Printing on the other size. An A4 file printed on Letter paper, or the other way round, needs "Fit" or "Shrink oversized pages" in the print dialog, or it loses an edge. Booklets have their own twist, covered in how to print a PDF as a booklet.
What the Number Measures, and the Limits
The size the inspector reports is the visible page: what a viewer shows and what prints. Technically that's the CropBox, which can be smaller than the MediaBox that describes the full sheet. If the page is rotated 90 degrees, width and height are reported as you see them, not as stored.
Two limits to know. The tool tells you what size pages are, not what's on them, so a Letter page with an A4-shaped scan inside still reads as Letter. And "Non-standard" covers sizes it doesn't name, such as B5, Executive or a 16:9 slide, so look those up yourself.
The file is read by pdf.js inside your browser tab and never uploaded. Only page dimensions are read, so even large files load quickly.
Frequently Asked Questions
How do I find the page size of a PDF?
Drop the file into Page Size Inspector to see every page in points, inches, mm or cm. In Acrobat, File, then Properties shows the size of the current page only.
What is A4 size in points?
A4 is 595.28 × 841.89 points, usually rounded to 595 × 842. That's 210 × 297 mm or about 8.27 × 11.69 inches.
Is my PDF A4 or Letter?
Check the width. A4 is 595 points (210 mm) wide and Letter is 612 points (8.5 in) wide. Page Size Inspector names the size for you, page by page.
How many points are in an inch in a PDF?
Exactly 72. One PDF unit is 1/72 inch, so an 8.5 × 11 inch page measures 612 × 792 points.
Can one PDF have pages of different sizes?
Yes. Each page carries its own size, so merged files often mix A4, Letter and scanned pages. The inspector lists each size with its pages, and Fix Page Size can make them uniform.
Need to know exactly what you're sending to the printer? Check your PDF's page sizes in your browser, every page, nothing uploaded.
