1. ISO 216 A & B series
Both series use a 1:√2 ratio. Cutting in half yields the next size at the same aspect ratio.
| Size | mm | Use |
|---|---|---|
| A0 | 841 × 1189 | Large poster, 1 m² area |
| A1 | 594 × 841 | Poster, blueprint |
| A2 | 420 × 594 | Mid poster |
| A3 | 297 × 420 | Catalog cover |
| A4 | 210 × 297 | Flyer, document standard |
| A5 | 148 × 210 | Half flyer, small booklet |
| A6 | 105 × 148 | Postcard, DM |
| B0 | 1000 × 1414 | Concert/movie poster |
| B5 | 176 × 250 | Books, textbooks |
2. Business cards — regional standards
- Korea 90×50mm — Domestic default.
- US 3.5×2 inch (88.9×50.8mm) — North America.
- EU ISO 7810 ID-1 (85×55mm) — Credit-card ratio.
3. mm · inch · px conversion (300dpi)
Formula: px = mm / 25.4 × dpi.
| mm | inch | 72dpi px | 300dpi px |
|---|---|---|---|
| 90 (card W) | 3.54" | 255 | 1063 |
| 148 (A6 W) | 5.83" | 419 | 1748 |
| 210 (A4 W) | 8.27" | 595 | 2480 |
| 297 (A4 H) | 11.69" | 842 | 3508 |
| 420 (A3 H) | 16.54" | 1191 | 4961 |
| 594 (A1 W) | 23.39" | 1684 | 7016 |
4. DPI picker
- 72 dpi — Screen, very large banners (viewed from 3m+).
- 150 dpi — A1-size posters (1m+ viewing).
- 300 dpi — Print default. Cards, flyers, books.
- 600 dpi — Fine-art catalogs, high-end.
5. CMYK vs RGB
- CMYK — Ink on paper.
- RGB — Light on screen or LED signage.
Converting RGB to CMYK drops saturation by 10–20%. Start in CMYK if the final output is paper.
6. Bleed defaults
- Business card / postcard — 2–3mm
- Flyer / poster — 3mm
- Banner / outdoor — 10–20mm
- Die-cut sticker — 2mm
7. Large banners
Use lower DPI to keep file size sane. A 4m banner at 300dpi would be 47,244 × 7,087 px — overkill. 72dpi (11,339 × 1,701 px) is visually identical at 10m viewing distance.
8. File formats
- PDF/X-1a — Industry-standard exchange.
- AI — Legacy press workflow, outline text.
- TIFF 300dpi CMYK — Photo-heavy output.
9. Checklist
- Confirm size (A4, card 90×50, banner 2×0.6m?).
- Pick DPI (300 for print, 72–150 for large format).
- Switch to CMYK.
- Create document including bleed.
- Keep critical content 3–5mm inside the trim.
- Export as PDF/X-1a, cross-check with vendor spec.