ISO 216 Paper Sizes — The Global Standard for the Metric World
Introduction
Paper is something we use every day, but its sizes are far from arbitrary. In most countries that follow the metric system, the dimensions of writing paper, documents, and many printed items are defined by the international standard ISO 216. This system covers the A series, the B series, and methods for indicating machine direction (grain). With its elegant mathematical basis, ISO 216 makes paper more consistent, efficient, and scalable than competing systems such as the North American “Letter” and “Legal” formats (ISO, 2007).
1. The A Series — Everyday Paper Sizes
The A series is the core of ISO 216.
- A0 has an exact area of 1 m².
- Each subsequent size is created by halving the sheet parallel to its shorter side.
- All sizes retain the √2 aspect ratio, which makes them perfectly scalable.
Dimensions of the A series
| Size | Dimensions (mm) |
|---|---|
| A0 | 841 × 1189 |
| A1 | 594 × 841 |
| A2 | 420 × 594 |
| A3 | 297 × 420 |
| A4 | 210 × 297 |
| A5 | 148 × 210 |
| A6 | 105 × 148 |
| A7 | 74 × 105 |
| A8 | 52 × 74 |
| A9 | 37 × 52 |
| A10 | 26 × 37 |
Common uses:
- A4: the global standard for letters, reports, and forms.
- A3: diagrams, posters, often folded to A4.
- A5: booklets and smaller manuals.
- A6: postcards.
2. The B Series — Intermediate Sizes
The B series provides dimensions between A sizes. B0 has an area of √2 m², and the rest follow the same halving principle.
Dimensions of the B series
| Size | Dimensions (mm) |
|---|---|
| B0 | 1000 × 1414 |
| B1 | 707 × 1000 |
| B2 | 500 × 707 |
| B3 | 353 × 500 |
| B4 | 250 × 353 |
| B5 | 176 × 250 |
| B6 | 125 × 176 |
| B7 | 88 × 125 |
| B8 | 62 × 88 |
| B9 | 44 × 62 |
| B10 | 31 × 44 |
Common uses:
- B5: academic journals and smaller books.
- B4: larger books.
- B7 and smaller: compact booklets or tickets.
3. Long Sizes — Practical Everyday Formats
ISO 216 also defines “long sizes,” created by dividing A sheets into equal strips parallel to the short side:
- ⅓ A4 (99 × 210 mm): perfect for DL envelopes, widely used in business correspondence.
- ¼ A4 (74 × 210 mm): common for tickets and slips.
- ⅙ A7 (13 × 74 mm): used for labels and small tags.
4. Machine Direction (Grain)
Paper has a “grain” that affects folding and binding. ISO 216 requires that sizes be expressed in millimetres, with the second dimension representing the machine direction.
- Long-grain (LG): the long side runs with the grain.
- Short-grain (SG): the short side runs with the grain.
Examples:
- “297 × 210 mm SG” indicates a short-grain A4 sheet.
- “A2 LG” means an A2 sheet with long-grain orientation.
5. Tolerances
ISO 216 specifies how close the cut dimensions must be:
- Up to 150 mm: ± 1.5 mm
- 150–600 mm: ± 2 mm
- Above 600 mm: ± 3 mm
Measurements are taken under the standard testing atmosphere defined in ISO 187 (ISO, 2007).
6. The Special Case of JIS B5
In Japan and some East Asian markets, the Japanese Industrial Standard (JIS) B series is used instead of ISO B. While both share the √2 ratio, their dimensions differ slightly.
- ISO B5: 176 × 250 mm
- JIS B5: 182 × 257 mm
Why JIS B5 is excellent
- Balanced size: It is larger than A5 but smaller than A4, ideal for notebooks, schoolbooks, and manuals.
- Publishing standard: Widely adopted for novels, textbooks, and academic journals in Japan.
- Portable but spacious: Offers more room than A5 without the bulk of A4.
- Versatility: Works equally well for handwriting, diagrams, and print layouts.
This makes JIS B5 the “sweet spot” size for many readers and writers (Japanese Standards Association, 2009).
JIS B Series (different from ISO B)
| Size | Dimensions (mm) |
|---|---|
| B0 | 1030 × 1456 |
| B1 | 728 × 1030 |
| B2 | 515 × 728 |
| B3 | 364 × 515 |
| B4 | 257 × 364 |
| B5 | 182 × 257 |
| B6 | 128 × 182 |
| B7 | 91 × 128 |
| B8 | 64 × 91 |
| B9 | 45 × 64 |
| B10 | 32 × 45 |
7. Why ISO 216 Is Superior to Other Systems
Compared to non-metric paper formats such as Letter (8.5 × 11 inches) and Legal (8.5 × 14 inches), ISO 216 offers:
- Perfect scaling: All sizes share the √2 ratio, so enlarging or reducing never distorts proportions.
- Predictable areas: Each size is half or double the one next to it, making calculations easy.
- Global reach: Adopted by nearly every metric country, ensuring compatibility.
- Efficiency: Covers everything from micro-labels to posters without awkward formats.
Conclusion
ISO 216 provides the world’s most rational and efficient paper system, balancing mathematical elegance with practical usability. With the addition of the JIS B5 format in East Asia, the system serves global needs from office documents to publishing.
References
International Organization for Standardization. (2007). ISO 216:2007—Writing paper and certain classes of printed matter — Trimmed sizes — A and B series, and indication of machine direction. ISO.
Japanese Standards Association. (2009). JIS P 0138: Japanese paper sizes. JSA.