Every paper size, measured to the millimetre
A4 is 210 × 297 mm, a DL envelope 110 × 220 mm, an SRA3 press sheet 320 × 450 mm. This site lists every ISO A, B and C size in millimetres, centimetres, inches and pixels, compares them with US Letter and Legal, and covers envelopes, printing, packaging and ten calculators that do the maths for you.
One A0 sheet of exactly one square metre, divided to scale. Tap or click a field to open that size.
The sizes people look up most
Each page gives the dimensions in every unit, the pixels you need for print, the weight of one sheet and the envelope that fits.
All paper sizes in one chart, also as a free CSV and JSON download.
Envelopes
An A4 sheet folded into thirds goes into a DL envelope, folded twice into C6 and flat into C4. The envelope guide lists every size with the paper it is made for and shows where the window sits.
Printing
Three millimetres of bleed, 300 dpi, a PDF/X file and the right colour profile: with these four things your files go through a print shop without a phone call. Plus fold types with panel widths, paper weights and paper types.
Packaging
The Euro pallet measures 1200 × 800 mm, and most retail boxes are fractions of it. If you know the 600 × 400 mm module, you can plan boxes that fill a pallet without gaps.
Calculators and tools
Free, no sign-up, and your input never leaves your browser.
- Size converterPick a paper size and get every unit at once: millimetres, centimetres, inches, points and pixels at any resolution, portrait or landscape.
- Size finderEnter width and height and find the closest standard paper size, with the difference in millimetres.
- Size comparisonOverlay up to four paper sizes to scale, for example A4, Letter and C4, and read the differences in millimetres.
- Scaling factorThe percentage to scale A4 to A3, A5 or any other size. Calculator plus the full table from A0 to A10.
- Envelope finderChoose your paper size and fold and get the envelopes that fit, with the spare room in millimetres. Works for A4, A5, A6, Letter and custom sizes.
- Paper weight calculatorWork out the weight of sheets, a stack or a mailing from size, gsm and sheet count, and see the matching Deutsche Post letter class.
- Imposition calculatorFind out how many finished pieces fit on a press sheet such as SRA3 or 70 × 100 cm, including bleed and gutter, with a layout sketch.
- Bleed calculatorEnter trim size and bleed to get the document size, safe area and pixel dimensions for your print file.
- Pixels to cmConvert pixels to centimetres and back at any resolution, with tables for 72, 150 and 300 dpi and advice on image size for print.
- Inches to cmOne inch is exactly 2.54 cm. Convert inches to centimetres and back, with a table, fractions like 3/8 inch and common sizes.
Why A4 is exactly 210 × 297 mm
The idea predates the standard by more than a century. In 1786 the physicist Georg Christoph Lichtenberg wrote that a sheet should relate like the side of a square to its diagonal. Fold such a sheet in half and the half has the same shape again.
Walter Porstmann turned this into the German standard DIN 476 in 1922. He fixed the area of the starting sheet at one square metre, and four halvings later you arrive at the sheet that now sits in almost every printer on the planet.
US sizes, books, photos and standards
North America uses Letter and Legal, Japan has its own B series, and books and photos follow traditions of their own. The knowledge section explains the standards behind each size, the German business letter format DIN 5008 and a glossary of print terms.
Frequently asked questions
What are ISO paper sizes?
Standardised paper sizes defined in ISO 216. They started in Germany in 1922 as DIN 476, which is why they are often called DIN sizes. The A series covers paper and print, the B series posters and envelopes, the C series envelopes.
How big is A4?
A4 is 210 × 297 mm, which is 21 × 29.7 cm or 8.27 × 11.69 inches.
What aspect ratio do ISO sizes have?
All A, B and C sizes have an aspect ratio of 1 to the square root of 2, about 1 to 1.414. Cut a sheet in half and it keeps the same shape.
Which countries do not use A4?
The United States and Canada use Letter (8.5 × 11 in). Letter is also common in parts of Latin America and the Philippines.