Web page to PDF: paper sizes, margins and print CSS

What size is A4 in pixels?

A4 is 794 × 1123 CSS pixels and US Letter is 816 × 1056. CSS fixes the pixel at 1/96 of an inch and the point at 1/72 of an inch, so every paper size has exactly one size in pixels and one in points, whatever the resolution of the printer.^[2]

• px = inches × 96

  8.5 in × 96 = 816 px

• px = mm × 96 / 25.4

  210 mm × 96 / 25.4 = 793.70 px

• pt = inches × 72

  the same as px × 0.75

• A03179 × 4494 px · 2384 × 3370 pt841 × 1189 mm · 33.11 × 46.81 in
• A12245 × 3179 px · 1684 × 2384 pt594 × 841 mm · 23.39 × 33.11 in
• A21587 × 2245 px · 1191 × 1684 pt420 × 594 mm · 16.54 × 23.39 in
• A31123 × 1587 px · 842 × 1191 pt297 × 420 mm · 11.69 × 16.54 in
• A4794 × 1123 px · 595 × 842 pt210 × 297 mm · 8.27 × 11.69 in
• A5559 × 794 px · 420 × 595 pt148 × 210 mm · 5.83 × 8.27 in
• A6397 × 559 px · 298 × 420 pt105 × 148 mm · 4.13 × 5.83 in
• Letter816 × 1056 px · 612 × 792 pt215.9 × 279.4 mm · 8.5 × 11 in
• Legal816 × 1344 px · 612 × 1008 pt215.9 × 355.6 mm · 8.5 × 14 in
• Tabloid1056 × 1632 px · 792 × 1224 pt279.4 × 431.8 mm · 11 × 17 in

Portrait, width × height. Pixels and points are rounded to the nearest whole number and inches to two decimals. Only the North American pixel figures are exact, because those sizes are defined in inches. CSS has size keywords for ten sheets (A5, A4, A3, B5, B4, JIS-B5, JIS-B4, letter, legal, ledger); any other sheet is written as two lengths, such as size: 105mm 148mm.^[3] Chromium-based tools define the A sizes in inches rounded to two decimals (A4 as 8.27 × 11.7 in), so a page they report can differ from the ISO figure by one pixel.^[8]

The print CSS cheat sheet

Nine pieces of CSS control how a page prints: the sheet, the margins, where pages break, what keeps its colour and what repeats. The versions are the first release of each browser with support, from MDN compatibility data.^[12]

• Paper size and margins

  Sets the sheet and the margin for every page of the document.^[1][3][12]

  /* also: letter, A3 landscape */
  @page {
    size: A4;
    margin: 20mm;
  }

  CSS has keywords for A5, A4, A3, B5, B4, JIS-B5, JIS-B4, letter, legal and ledger. Any other sheet is written as two lengths. Safari does not support the portrait and landscape keywords.

  Chrome 15+Firefox 95+Safari 18.2+

• A different first page

  Styles only the first printed page. :left and :right style the two sides of a spread.^[1][12]

  /* room for a letterhead on page one */
  @page :first {
    margin-top: 40mm;
  }

  Firefox does not support :left and :right.

  Chrome 18+Firefox 116+Safari 6+

• Page breaks

  Forces a break before an element, or keeps a block or a heading and its text together.^[5][12]

  /* start on a new page */
  h2 { break-before: page; }
  
  /* never split in two */
  figure, tr { break-inside: avoid; }
  
  /* keep a heading with what follows */
  h2, h3 { break-after: avoid-page; }

  Firefox does not support avoid-page (or plain avoid) on break-before and break-after; break-inside: avoid works in all three.

  Chrome 50+Firefox 65+Safari 10+

• Legacy page-break aliases

  The older page-break-* properties still work: browsers treat them as aliases of break-*.^[5]

  /* the same as break-before: page */
  h2 { page-break-before: always; }
  
  /* the same as break-inside: avoid */
  figure { page-break-inside: avoid; }

  The alias maps always to page. Write both forms only if you must support very old engines.

  Chrome yesFirefox yesSafari yes

• Orphans and widows

  Sets the fewest lines of a paragraph that may stand alone on either side of a break. Both start at 2.^[6][12]

  p {
    orphans: 3;  /* lines left at the bottom */
    widows: 3;   /* lines carried to the top */
  }

  Firefox supports neither property.

  Chrome 25+Firefox noSafari 1.3+

• Keep backgrounds and colours

  Tells the browser not to drop or alter the backgrounds and colours of these elements in print.^[7][12]

  .badge, thead th {
    /* the prefixed line is for Chrome before 136 */
    -webkit-print-color-adjust: exact;
    print-color-adjust: exact;
  }

  Chrome took the -webkit- prefix from version 17 and the plain name from 136. Chrome and Safari do not print the background of the body element itself, and a user setting can still override the property.

  Chrome 136+Firefox 97+Safari 15.4+

• Rules for paper only

  Applies only when the page is printed or saved as a PDF: hide the navigation, set type in points, print link addresses.^[11]

  @media print {
    nav, aside, .cookie-banner {
      display: none !important;
    }
    body { font-size: 11pt; }
    a[href^="http"]::after {
      content: " (" attr(href) ")";
    }
  }

  Chrome yesFirefox yesSafari yes

• Repeat table headers

  A real thead is a table header group, which print engines may repeat on every page the table spans.^[10]

  <table>
    <thead><tr><th>Item</th><th>Price</th></tr></thead>
    <tbody>...</tbody>
  </table>

  CSS says "may", so treat a repeated header as likely, not guaranteed, and test in the engine you print with. A header built from div elements never repeats.

• Running header and page numbers

  Puts text and page numbers in the 16 margin boxes around the page area.^[1][4][12]

  @page {
    @top-center {
      content: "Quarterly report";
    }
    @bottom-right {
      content: counter(page) " / " counter(pages);
    }
  }

  Chrome 131 and later only. The margin has to be wide enough to hold the text: with a zero margin there is nowhere to draw it.

  Chrome 131+Firefox noSafari no

• What does not work everywhere

  Page margin boxes work only in Chrome 131 and later.^[4] Firefox supports neither orphans nor widows, and Safari learned @page size only in version 18.2.^[12] A PDF made by a Chromium-based service gets Chrome behaviour whatever browser the reader uses.

  How to read the badges: a number is the first version of that browser with support, and a grey badge means no released version supports it as of October 2026. A card without badges has no entry in the compatibility data.

PDF options in the CurlShot API

CurlShot turns a web page into a PDF when a request carries format=pdf. The defaults are A4, portrait, no margin, backgrounds printed and the screen layout, and a PDF always covers the whole page from top to bottom.

The paper comes from pdf_paper_format. The API adds no header, footer or page numbers of its own, and it has no separate zoom option for PDF. Two image options, selector and clip_*, are refused together with format=pdf.

curl "https://curlshot.com/api/v1/screenshot?access_key=YOUR_ACCESS_KEY\
&url=https://example.com\
&format=pdf\
&media_type=print\
&pdf_paper_format=a4\
&pdf_margin=20mm" \
  --output page.pdf