Application scope of different standard paper size.


A Series (The Everyday Standard): The base A0 sheet has an area of 1 square meter. Each subsequent size (A1, A2, A3, etc.) is created by halving the previous sheet parallel to its shorter side.
A0, 841 × 1189 mm. Technical drawing, large posters, maps. The standard size for architectural and engineering plans.
A1, 594 × 841 mm. Technical drawing, flip charts, theater posters.
A2, 420 × 594 mm. Medium-sized posters, architectural drawings, diagrams, flip charts.
A3, 297 × 420 mm. Tabloid magazines, small posters, diagrams, CAD drawings. Common for large-format printing in offices (spreadsheets, technical manuals).
A4, 210 × 297 mm. The universal standard for business. Used for letters, documents, reports, forms, magazines, brochures, and laser printers.

B Series (The "In-Between" and Special Use Series): The B-series sizes are geometric means between the A-series sizes. They are less common but fill important niche roles.
B0, 1000 × 1414 mm. Large posters, wall charts. Used when an intermediate size between A0 and the larger 2A0 is needed.
B1, 707 × 1000 mm. Newspapers, extended posters.
B2, 500 × 707 mm. Musical posters, medium-sized newspapers.
B3, 353 × 500 mm. Books, newspapers.
B4, 250 × 353 mm. Books, music scores. Also a common size for external envelopes.

C Series (The Envelope Series): Defined in ISO 269, the C-series is specifically for envelopes. A C4 envelope is designed to hold an unfolded A4 sheet, a C5 holds an A4 sheet folded once (A5), and a C6 holds an A4 sheet folded twice (A6).


This system uses traditional, non-harmonic sizes with arbitrary aspect ratios. The naming is based on historical uses.
Letter: 216 × 279 mm. The standard for all business and academic documents in North America. Used for everything from printing to photocopying. Equivalent to A4.
Legal: 216 × 356 mm. Legal documents, contracts. The extra length provides space for formal headers, footers, and signatures.
Tabloid (Ledger): 279 × 432 mm. Newspapers, small posters, brochures, technical drawings. Equivalent to A3. "Ledger" is used when the orientation is landscape.
Executive: 184 × 267 mm. Formal business stationery, executive letterheads. Less common than Letter size.

Note: The A-series is a perfectly scalable system for general purpose and technical use. The North American system is based on traditional, fixed sizes for specific tasks. Your geographic location and the specific end-use of the document are the primary factors in choosing the correct standard paper size.