| Size | mm | inches | px (300DPI) |
|---|
ISO 216 is the international paper size standard adopted by most countries (except North America). The core design principle: each size has a √2:1 (≈1.414:1) aspect ratio, so folding preserves proportions. A0 has exactly 1 square meter area, and each subsequent size halves the area.
A Series: The most common office and printing standard. A4 (210×297mm) is the most widely used paper size for daily printing and documents.
B Series: Intermediate sizes between A series, used for posters, books, and specialized printing. B5 (176×250mm) is common for books.
C Series: Designed for envelopes. C4 fits unfolded A4, C5 fits A5 or folded A4, C6 fits A6 or folded A5.
DPI determines print quality: 300 DPI for standard high-quality printing, 72-96 DPI for screen display, 150 DPI for newspapers, 600+ DPI for professional photo printing. Formula: pixels = mm ÷ 25.4 × DPI.
A4 paper is the most common size in the ISO 216 standard, measuring 210 × 297 mm (about 8.27 × 11.69 inches). It's part of the A-series and is widely used for printing, copying, office documents, and everyday writing. At 300 DPI, pixel dimensions are 2480 × 3508 pixels.
A-series (e.g., A4) is for general office and printing. B-series (e.g., B5) provides intermediate sizes between A-series, often used for books and posters. C-series (e.g., C4) is designed for envelopes that hold A-series paper without folding.
Choose based on use: A4 for standard documents, letters, and printing; A3 for posters, charts, and large tables; A5 for brochures and notebooks; B5 for books; C4/C5 for envelopes. For photos, common sizes include 4×6 inches (10×15cm) and 5×7 inches (13×18cm).
DPI (Dots Per Inch) determines print quality. Use 300 DPI for high-quality printing; 72-96 DPI for screen display; 150-200 DPI for newspaper printing; 600+ DPI for high-quality photo printing. Pixel size = mm size ÷ 25.4 × DPI.
A0 paper has an area of 1 square meter (841×1189mm). A1 is 0.5 m² (594×841mm), and so on. Each step down (A0→A1) halves the area by folding the long side. This consistent ratio makes scaling between sizes perfect for printing.
ISO 216 is the international paper size standard, covering A, B, and C series. Published in 1975, it's used in most countries (except North America which uses Letter, Legal, etc.). The core principle is the √2:1 aspect ratio, maintaining proportions when folded.