PDF Page Sizes

Every standard page size in the unit a PDF actually stores — PostScript points — alongside millimetres, inches and pixel dimensions at four resolutions.

What unit does a PDF page use?

PostScript points. One point is exactly 1/72 inch, and every page box inside a PDF is written in them — which is why an A4 page is stored as 595.28 × 841.89 and a Letter page as exactly 612 × 792. Points are a physical unit, not a pixel count: a PDF page has a real size in inches and no inherent resolution. Pixels only enter the picture when the page is rasterised, and then the number depends entirely on the DPI you pick, which is why the same A4 page is 595 px wide at 72 DPI and 2,480 px wide at 300 DPI.

ISO A series

The international standard, used everywhere except North America. Every size has the same 1:√2 proportions, so halving the long side of one gives the next size down and scaling between them never changes the shape of the page.

ISO A series page sizes
Size	Points (PDF units)	Millimetres	Inches	72 DPI	96 DPI	150 DPI	300 DPI
A0	2383.94 × 3370.39	841 × 1189 mm	33.11 × 46.81 in	2384 × 3370	3179 × 4494	4967 × 7022	9933 × 14043
A1	1683.78 × 2383.94	594 × 841 mm	23.39 × 33.11 in	1684 × 2384	2245 × 3179	3508 × 4967	7016 × 9933
A2	1190.55 × 1683.78	420 × 594 mm	16.54 × 23.39 in	1191 × 1684	1587 × 2245	2480 × 3508	4961 × 7016
A3	841.89 × 1190.55	297 × 420 mm	11.69 × 16.54 in	842 × 1191	1123 × 1587	1754 × 2480	3508 × 4961
A4	595.28 × 841.89	210 × 297 mm	8.27 × 11.69 in	595 × 842	794 × 1123	1240 × 1754	2480 × 3508
A5	419.53 × 595.28	148 × 210 mm	5.83 × 8.27 in	420 × 595	559 × 794	874 × 1240	1748 × 2480
A6	297.64 × 419.53	105 × 148 mm	4.13 × 5.83 in	298 × 420	397 × 559	620 × 874	1240 × 1748
A7	209.76 × 297.64	74 × 105 mm	2.91 × 4.13 in	210 × 298	280 × 397	437 × 620	874 × 1240
A8	147.4 × 209.76	52 × 74 mm	2.05 × 2.91 in	147 × 210	197 × 280	307 × 437	614 × 874
A9	104.88 × 147.4	37 × 52 mm	1.46 × 2.05 in	105 × 147	140 × 197	219 × 307	437 × 614
A10	73.7 × 104.88	26 × 37 mm	1.02 × 1.46 in	74 × 105	98 × 140	154 × 219	307 × 437

A0 — One square metre of area. Architectural and engineering plots.
A1 — Posters and large drawings.
A2 — Drawings, medium posters.
A3 — Two A4 pages side by side. Spreadsheets and drawings.
A4 — The default document size everywhere except North America.
A5 — Notebooks, flyers, booklets.
A6 — Postcards.

North American sizes

Defined in whole and half inches rather than millimetres, which is why their metric equivalents carry a decimal place.

North American page sizes
Size	Points (PDF units)	Millimetres	Inches	72 DPI	96 DPI	150 DPI	300 DPI
Letter	612 × 792	215.9 × 279.4 mm	8.50 × 11.00 in	612 × 792	816 × 1056	1275 × 1650	2550 × 3300
Legal	612 × 1008	215.9 × 355.6 mm	8.50 × 14.00 in	612 × 1008	816 × 1344	1275 × 2100	2550 × 4200
Tabloid / Ledger	792 × 1224	279.4 × 431.8 mm	11.00 × 17.00 in	792 × 1224	1056 × 1632	1650 × 2550	3300 × 5100
Executive	521.86 × 756	184.1 × 266.7 mm	7.25 × 10.50 in	522 × 756	696 × 1008	1087 × 1575	2174 × 3150
Half Letter	396 × 612	139.7 × 215.9 mm	5.50 × 8.50 in	396 × 612	528 × 816	825 × 1275	1650 × 2550
Junior Legal	360 × 576	127 × 203.2 mm	5.00 × 8.00 in	360 × 576	480 × 768	750 × 1200	1500 × 2400

Letter — 8.5 × 11 in. The North American default.
Legal — 8.5 × 14 in. Contracts and legal filings.
Tabloid / Ledger — 11 × 17 in. Ledger is the landscape orientation of the same sheet.
Executive — 7.25 × 10.5 in.
Half Letter — 5.5 × 8.5 in. Also called Statement.
Junior Legal — 5 × 8 in.

ISO B series

Sits between adjacent A sizes. B5 is the usual choice for books and conference proceedings, where A5 is a little small and A4 a little large.

ISO B series page sizes
Size	Points (PDF units)	Millimetres	Inches	72 DPI	96 DPI	150 DPI	300 DPI
B4	708.66 × 1000.63	250 × 353 mm	9.84 × 13.90 in	709 × 1001	945 × 1334	1476 × 2085	2953 × 4169
B5	498.9 × 708.66	176 × 250 mm	6.93 × 9.84 in	499 × 709	665 × 945	1039 × 1476	2079 × 2953
B6	354.33 × 498.9	125 × 176 mm	4.92 × 6.93 in	354 × 499	472 × 665	738 × 1039	1476 × 2079

B5 — Common for books and academic proceedings.

Why is A4 210 × 297 mm and not a round number?

Because A0 is defined as the rectangle with an area of exactly one square metre and sides in the ratio 1:√2, which comes out at 841 × 1189 mm. Each smaller size halves the long side, and the standard rounds down to the whole millimetre at every step. Carried through to A4 that gives 210 × 297 mm rather than the exact 210.224 × 297.302 the ratio would produce. The same rounding is why halving A4’s 297 mm yields A5 at 148 mm and not 148.5.

How many pixels is an A4 page?

It depends on the resolution, and the question has no answer without one. At 72 DPI an A4 page is 595 × 842 px, which matches its point dimensions because both units are 1/72 inch. At 96 DPI — the nominal Windows screen resolution — it is 794 × 1123 px. At 150 DPI, a reasonable setting for on-screen reading of a scan, 1240 × 1754 px. At 300 DPI, the usual print standard, 2480 × 3508 px. The formula is millimetres ÷ 25.4 × DPI.

How do you find out what size a PDF’s pages actually are?

Read them off the file. The PDF Metadata Viewer reports the dimensions of every page, names the matching stock where there is one, and groups pages that share a size — so a document that mixes A4 body pages with A3 foldouts shows both rather than one number. It runs in your browser, so the file is not uploaded.

Can you change a PDF’s page size?

You can change the page boundaries, but not rescale the content by resizing the box. Crop PDF trims each page by an exact number of points per side, which is how you turn an over-wide scan into a clean A4. When you are building a PDF from images instead, the image converters let you choose the output page size and margin up front, which is the right place to make the decision.