Paper Sizes: A, B and US Charts in Inches, mm and cm

Paper size guides

Standard paper sizes at a glance

These are the sizes you are likely to meet at a printer, an office supply store or in a print dialog. The ISO sizes are defined in millimeters and the US sizes in inches, so each table converts in one direction only.

A3 297 × 420 mmTabloid 279.4 × 431.8 mmA4 210 × 297 mmLetter 215.9 × 279.4 mm

A-series paper sizes (ISO 216)

The A series starts from A0, a sheet of one square meter, and halves the area at each step while keeping the side ratio at 1:√2 (1:1.414). That ratio is why an A3 sheet folds into two A4 sheets with identical proportions, and why a photocopier enlarges A4 to A3 at 141% without cropping. The A4 paper size guide explains the math in detail.

A3 size in inches and cm

A3 is 297 × 420 mm, which is 29.7 × 42 cm or 11.69 × 16.54 inches. It is exactly two A4 sheets side by side along the long edge. At 300 DPI an A3 file needs 3508 × 4961 pixels.

A3+ (Super A3)

A3+ is not an ISO size. It is a printer-industry format of 329 × 483 mm (13 × 19 in), the largest sheet many desktop photo printers accept. The extra margin lets you print an A3 image edge to edge and trim it, or print a 12 × 18 in photo with a border.

US and Canadian paper sizes

North American sizes grew out of traditional mill sizes, not a single formula. Letter and Legal share a width of 8.5 in, which is why a Legal sheet fits a Letter-width printer tray but needs a longer tray setting. Canada uses the same sheets; its metric P-series standard (P4 = 215 × 280 mm) is a rounded Letter and is rarely labeled as such in shops.

The 8.5 × 13 in Folio sheet is the everyday "long" paper in the Philippines and parts of Southeast Asia, where it is sold as long bond or F4. Sheets labeled F4 vary slightly by country (210 or 215 mm wide, 330 mm long), so check the pack before setting up a print job.

B-series and C-series sizes

The B series fills the gaps between A sizes: each B sheet is the geometric mean of the A size above and below it, so B4 (250 × 353 mm) sits between A4 and A3. B sizes are used for books, passports (B7), posters (B1, B2) and some notebooks. The C series is for envelopes and is sized so an A sheet slides into the C envelope of the same number.

Which envelope suits which sheet, including US Letter and Legal, is covered in matching envelopes to paper sizes. For every envelope format with its numbering, see the main envelope size chart.

Japanese B sizes (JIS)

Japan uses the ISO A series but its own B series, defined in JIS P 0138, with sheets about 3% larger on each side. A notebook or copier tray labeled B5 in Japan, China or Korea is usually the JIS size.

Engineering and architectural sheet sizes

Drawings in the US use two inch-based ladders. ANSI sizes double from Letter, alternating between two aspect ratios. Architectural (Arch) sizes keep near 3:4 or 2:3 ratios and are the standard for building plans and many large-format posters.

Arch C (18 × 24 in) and Arch D (24 × 36 in) are the same as two of the most popular poster sizes, so many print shops quote posters in these dimensions. See standard poster sizes for how they are used on the wall.

A sizes vs US sizes: closest equivalents

No ISO size matches a US size exactly. These are the pairs that substitute for each other in practice, with the difference that matters when you print or bind.

How many sheets fit on a larger sheet

Commercial printers run jobs on big sheets and cut them down. Because each A size is half the one above, the count always doubles: two A4 on A3, four on A2, eight on A1, sixteen on A0. The same logic answers questions like "what size fits four A3 sheets" (A1) or how many A5 notebook pages come from one sheet: an A4 sheet folded once makes a 4-page A5 section, printed two pages per side.

Presses print on slightly oversize stock so the image can bleed off the edge. ISO 217 defines these untrimmed sizes: SRA3 is 320 × 450 mm and SRA4 is 225 × 320 mm, which leaves room for a 3 mm bleed plus crop marks around A3 and A4 jobs. In the US, Letter jobs with bleed are usually run on 12 × 18 in or 13 × 19 in sheets.

Paper weight: gsm vs US pounds

Paper thickness is sold by weight. The metric unit, grams per square meter (gsm), compares directly across all paper. The US pound system weighs a 500-sheet ream of a "basis size" that differs by paper type, so 20 lb bond and 50 lb text are nearly the same paper.

To convert: bond lb × 3.76 = gsm; text lb × 1.48 = gsm; cover lb × 2.70 = gsm. Home printers differ widely in the heaviest stock they accept, and the manual or rear feed usually takes thicker card than the main tray, so check the printer's spec sheet before buying cover stock.

Choosing a paper size

• Documents for one country: use that country's office size, Letter in North America and A4 elsewhere. Mail, binders and filing cabinets are built around it.
• Documents for both markets: design on A4 or Letter with side margins of at least 20 mm and a bottom margin of at least 25 mm, so either paper prints cleanly.
• Booklets: fold the office size in half. Letter folds to 5.5 × 8.5 in and A4 folds to A5, so a home printer can make both.
• Notes and journals: A5 and B5 are the common international notebook sizes; US school notebooks use Letter or composition sizes. See the notebook size chart.
• Posters and art prints: A3 to A0 outside the US, and 11 × 17, 18 × 24 or 24 × 36 in inside it. Pixel requirements for each are in the poster print-file guide, and photo formats are in photo print sizes.

Frequently asked questions