How to Read Paper Size Names (A4, B5, C5, DL, ANSI)
In the ISO system the letter gives the series and the number tells you how many times the base sheet was halved, so a bigger number means smaller paper. North American names such as Letter and Legal are traditional and are not numbered.
| Name | Meaning | Example |
|---|---|---|
| A series | ISO 216 sizes, A0 = 1 m² | A4: 210 × 297 mm |
| B series | ISO 216 sizes between the A sizes | B5: 176 × 250 mm |
| C series | ISO 269 envelope sizes | C5: 162 × 229 mm |
| DL | Long envelope for A4 folded in three | DL: 110 × 220 mm |
| Letter / Legal / Tabloid | Traditional North American sizes | Letter: 8.5 × 11 in |
| ANSI A–E | US engineering drawing sizes (A = Letter, B = Tabloid) | ANSI D: 22 × 34 in |
| ARCH A–E | US architectural drawing sizes | ARCH D: 24 × 36 in |
The ISO system
In the ISO system a larger number means a smaller sheet. A0 is the largest and A10 the smallest, and each step halves the previous sheet. The B and C series use the same numbering, with B sizes between A sizes and C sizes designed as envelopes for A sizes.
North American names
Names such as Letter, Legal and Tabloid are traditional and are defined in inches. They are not part of a numbered family, so you cannot tell the size from the name alone. ANSI A (Letter) and ANSI B (Tabloid) connect these names to the engineering drawing series ANSI C, ANSI D and ANSI E.
Check which standard a size belongs to
Some names exist in more than one system. For example, Japanese JIS B sizes differ from ISO B sizes. When a product or print shop quotes a size, check the millimetre or inch dimensions as well as the name.
Frequently asked questions
Is B5 the same everywhere?
No. ISO B5 is 176 × 250 mm, while the Japanese JIS B5 size is a different size. Always check the dimensions.
What is the difference between Tabloid and Ledger?
They are the same 11 × 17 inch sheet. Tabloid refers to portrait orientation and Ledger to landscape.
Related
- How ISO Paper Sizes Work (A, B and C)Why A4 is 210 × 297 mm
- A4 Paper Size210 × 297 mm
- Letter Paper Size8.5 × 11 in
- Paper Size Cheat Sheet: All Standard SizesEvery size on one page
Last updated: 2026-10-03