A4 paper size and dimensions

A4 is the paper in almost every printer outside North America. It was standardised in Germany in 1922 and is now defined internationally by ISO 216. The dimensions above are for portrait orientation. Turn the sheet and you have A4 landscape at 297 × 210 mm.

A4 in every unit

The point values matter in layout software such as InDesign, Affinity Publisher or Scribus. A PDF page in A4 is exactly 595 × 842 points.

A4 in pixels for screen and print

A sheet of paper has no pixels. How many pixels an image needs depends on the resolution it is printed at. Print shops work with 300 dpi as the rule, which gives 2480 × 3508 pixels for A4, about 8.7 megapixels.

A 12-megapixel phone photo (4032 × 3024 pixels) is plenty for an A4 print: on the long side it reaches roughly 345 dpi. You only run short if you crop heavily. When 150 dpi is enough and when it is not is covered under print resolution.

Where A4 comes from

All A sizes descend from one sheet with an area of exactly one square metre, A0 at 841 × 1189 mm. Halve it across the long side and you get A1. Halve that and you get A2, and so on. After four halvings you arrive at A4, so an A4 sheet is one sixteenth of a square metre.

The trick is the aspect ratio of 1 to √2. Only with this ratio does the half keep the shape of the whole. That is why A4 shrinks to A5 at 71 % and grows to A3 at 141 % with no borders and nothing cut off. The maths is on the aspect ratio page.

What A4 is used for

In offices A4 is the default: letters, invoices, quotes, forms, CVs and nearly everything that comes out of a printer. Schools use A4 exercise books and pads, and most ring binders, plastic sleeves and trays are made for A4.

In marketing A4 is often the starting point. Folded twice it becomes a DL leaflet (roll fold or Z fold), folded once a four-page A5 folder. Menus, price lists and notices often stay flat.

Which envelope fits A4?

For business letters, a DL window envelope is the usual choice. More combinations are worked out by the envelope finder.

How much does an A4 sheet weigh?

Standard copy paper is 80 gsm (grams per square metre). Because A4 is one sixteenth of a square metre, a sheet weighs just under 5 grams (4.99 g). A ream of 500 sheets comes to about 2.5 kg.

Postage often comes down to a single sheet. In Germany a standard letter may weigh up to 20 g, and three 80 gsm sheets in a DL envelope already sit right at that limit. The paper weight calculator works it out for any combination.

A4 vs US Letter

In the USA and Canada the standard sheet is Letter at 8.5 × 11 inches, or 215.9 × 279.4 mm. It is almost 6 mm wider and nearly 18 mm shorter than A4. Send a Letter PDF to a European printer and you get a white strip at the bottom; send an A4 PDF to an American one and the footer gets cut or the page shrinks. Tips for documents that work on both are in Letter vs A4.

Tolerances: is every A4 sheet exactly 210 × 297 mm?

Not quite. ISO 216 allows ±2 mm for dimensions between 150 and 600 mm, so an A4 sheet may be 208 to 212 mm wide and 295 to 299 mm tall. Branded paper is usually far closer than that, because printers feed skewed sheets otherwise.

Frequently asked questions