Paper size knowledge
The A4 sheet goes back to an idea from 1786 and became a standard in 1922. This section covers the standards behind the sizes, their history and the maths behind them, plus the German business letter layout DIN 5008, a glossary and answers to frequent questions.
Contents of this page
All pages in this section
- StandardsWhich standard covers which size? ISO 216, DIN 476-2, ISO 217, DIN 678, DIN 680, DIN 5008, ISO/IEC 7810 and ISO 3394 at a glance.
- HistoryHow an idea from 1786 became the A4 sheet: Lichtenberg, the French stamp law, Ostwald's world format, Porstmann and DIN 476.
- Aspect ratio 1:√2Why ISO paper has the ratio 1:1.414, how to calculate any size yourself and why 71 % and 141 % are the magic copier settings.
- DIN 5008 lettersThe German letter standard explained in English: margins, address field, information block, fold and punch marks for form A and form B.
- GlossaryPrint, paper and design terms explained in plain English, from bleed to Z fold, plus the abbreviations from CMYK to PDF/X.
- FAQShort, checked answers to the most common questions about paper sizes, envelopes, printing and paper, each linking to the full page.
- SourcesThe standards, historical sources and reference books this site relies on, and where to find the originals.
The ground rules
- Shape
- All ISO sizes have an aspect ratio of 1 to √2. A sheet cut in half keeps its shape, which is why you can copy between sizes at 71 % and 141 % without margins.
- Area
- A0 has an area of one square metre. A paper’s grammage is therefore the weight of an A0 sheet, and an A4 sheet of 80 g/m² paper weighs one sixteenth of that: 5 g.
- Series
- An A sheet fits a C envelope, which in turn fits a B envelope. The sizes are calculated that way.
- Rounding
- The dimensions are rounded down to whole millimetres and have tolerances of ±1.5 to ±3 mm.
Frequently asked questions
Who invented the A4 paper size?
The engineer Walter Porstmann developed the system, which was published as DIN 476 on 18 August 1922. Georg Christoph Lichtenberg had already described the idea behind the aspect ratio in 1786.
What does DIN stand for?
Originally “Deutsche Industrie-Norm” (German industrial standard). Today DIN stands for the Deutsches Institut für Normung, the German Institute for Standardisation.