Paper Sizes Explained (A, B, C, US)
Paper sizes are organised into internationally standardised series. The ISO A-series (A0–A8) is used in India and most of the world, with A4 (210 × 297 mm) being the everyday standard. The B-series is used for books and posters; the C-series for envelopes. The US Letter and Legal sizes are North American standards not used in Indian printing.
Ask for 'A4 paper' in any stationery shop in India and you will be understood immediately. But mention A3, B5, or DL and you may get a blank look — or a confident but incorrect answer. Paper size terminology is widely used but rarely fully understood, and the gaps in knowledge cause real problems: documents formatted for the wrong size, covers ordered too small, envelopes that do not fit the documents inside. This guide explains the most important paper size systems used in printing, with specific dimensions, practical use cases, and guidance on when each size is relevant for the kinds of documents printed in India.
The ISO A-Series: India's Standard
The A-series is defined by ISO 216 and is the standard in India, the UK, Europe, Australia, and most of the world. It is built on a single elegant principle: every sheet is √2 times longer than it is wide (approximately 1:1.414), and folding an A-series sheet in half gives the next size down.
| Size | Dimensions (mm) | Common Use |
|---|---|---|
| A0 | 841 × 1189 | Large technical drawings, architectural plans |
| A1 | 594 × 841 | Posters, engineering drawings |
| A2 | 420 × 594 | Medium posters, flip charts |
| A3 | 297 × 420 | Spreadsheets, double-page layouts, large diagrams |
| A4 | 210 × 297 | Documents, reports, theses, letters — everyday standard |
| A5 | 148 × 210 | Notebooks, small books, pocket guides, flyers |
| A6 | 105 × 148 | Postcards, notecards, small booklets |
| A7 | 74 × 105 | Small cards, pocket notebooks |
The ratio between consecutive A sizes is always √2, which means content scales perfectly when you move between them — an A4 design reduced to 50% fits A5 with no distortion.
The ISO B-Series: Books and Posters
The B-series fills in the gaps between A sizes. Each B size falls between the A size of the same number and the A size of the number above: B4 is between A4 and A3.
| Size | Dimensions (mm) | Common Use |
|---|---|---|
| B4 | 250 × 353 | Printed books, academic journals |
| B5 | 176 × 250 | Textbooks, novels, conference proceedings |
| B6 | 125 × 176 | Pocket books, paperback novels |
B5 is a popular book size in India — many university textbooks and academic journals use B5 format. If you want your self-published or printed book to match standard bookshelf dimensions, B5 or A5 are the go-to choices.
The ISO C-Series: Envelopes
The C-series is designed specifically for envelopes that hold A-series documents:
- C4 envelope: Holds an unfolded A4 sheet
- C5 envelope: Holds an A4 sheet folded once (= A5 size)
- C6 envelope: Holds an A4 sheet folded twice (= A6 size), or an A5 sheet folded once
- DL envelope: 110 × 220 mm — holds an A4 sheet folded into thirds; the standard business letter envelope
North American Sizes: When They Matter in India
US Letter (216 × 279 mm) and US Legal (216 × 356 mm) are North American standards. You will encounter them in PDFs created with American software defaults or documents from US clients. In India, these sizes are not stocked as standard paper — if you print a Letter-formatted document on A4, expect scaling or marginal clipping. Always convert to A4 before printing in India.
Choosing the Right Size for Your Document
- Everyday documents, reports, assignments, theses: A4
- Presentation slides printed as handouts: A4 landscape or A5
- Books, textbooks, personal journals: A5 or B5
- Posters and notice boards: A3 or A2
- Postcards, invitations: A6
- Business letters for envelope mailing: A4 document in DL or C5 envelope
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Frequently asked questions
- What is the most common paper size in India?
- A4 (210 × 297 mm) is the standard for virtually all documents in India — government forms, university submissions, business correspondence, and office reports all use A4. It is what every printer, copier, and print shop in India is set up for by default.
- What is the difference between A4 and A5?
- A5 (148 × 210 mm) is exactly half the area of A4. Fold an A4 sheet in half and you have A5. A5 is used for smaller booklets, pocket guides, prescription pads, and compact notebooks. For a printed book that fits comfortably in a bag, A5 is a popular choice.
- When would I need A3 printing?
- A3 is twice the size of A4 and is used for spreadsheets with many columns, detailed technical drawings, maps, posters for noticeboards, and documents where two A4 pages are presented as a side-by-side spread. Printster supports A3 printing — check availability when configuring your order.
- What is B5 paper and is it available in India?
- B5 (176 × 250 mm) is a standard book size used for textbooks, academic journals, and trade paperbacks. It is not as universally stocked as A4 in Indian print shops, but specialist printers and online services can usually accommodate B5 for book printing. Confirm availability with Printster before placing a book-size order.
- My PDF is US Letter size. Will Printster print it on A4?
- Yes, but Letter is slightly different from A4 (shorter and wider). The print system will scale or fit the content to A4 stock. For documents where margins and layout precision matter, convert your PDF to A4 in your source application before uploading.
- What envelope size fits an A4 letter?
- For an unfolded A4 sheet, use a C4 envelope. For an A4 sheet folded once (to A5 size), use a C5 envelope. For a standard business letter where the A4 sheet is folded into thirds, use a DL envelope (110 × 220 mm).