Paper Size Calculator

How Does the Formula Work?

The paper size calculator provides instant dimensions for every standard paper format used worldwide. Select from 23 paper sizes across four series — the ISO 216 A-series (A0 through A8), B-series (B0 through B5), C-series envelopes (C3 through C6), and US sizes (Letter, Legal, Tabloid, Executive) — and get dimensions in millimeters, centimeters, and inches, plus area and pixel dimensions at 72, 150, and 300 DPI for digital design. Paper size confusion costs businesses time and money through misprints, mismatched envelopes, and formatting errors. This calculator eliminates guesswork whether you are printing documents, designing graphics, ordering envelopes, or setting up page layouts.

The ISO 216 A-Series

The A-series is the most widely used paper size standard globally, adopted by every country except the US and Canada. Its design is mathematically elegant: A0 has an area of exactly 1 square meter (841 × 1189 mm). Each subsequent size is exactly half the previous one, created by cutting along the longer dimension. A1 is half of A0, A2 is half of A1, and so on. The magic is in the aspect ratio — 1:√2 (approximately 1:1.414). This ratio is preserved when halved, so every A-size has the same proportions. This means an A4 document scaled to A3 or shrunk to A5 retains its proportions perfectly with no cropping. A4 (210 × 297 mm) is the international standard for letters, documents, and office printing.

A4 vs US Letter — The Great Paper Divide

A4 (210 × 297 mm) and US Letter (216 × 279 mm, or 8.5 × 11 inches) are maddeningly similar but not identical. US Letter is wider (6 mm more) and shorter (18 mm less). This causes formatting issues when documents travel between the US and the rest of the world — margins shift, text reflows, and carefully designed layouts break. PDF files created for A4 may not print correctly on US Letter and vice versa. When preparing international documents, always specify the paper size explicitly and include appropriate margins. For safety, design documents with margins of at least 20 mm on all sides to accommodate both formats.

B-Series and C-Series

The B-series sizes are geometric means between consecutive A-series sizes — B4 is between A3 and A4 in area. B-series is used for books, posters, passports, and maps. Many countries use B5 (176 × 250 mm) for books and magazines. The C-series is specifically designed for envelopes: a C4 envelope (229 × 324 mm) fits an unfolded A4 sheet, C5 (162 × 229 mm) fits an A4 folded once, and C6 (114 × 162 mm) fits an A4 folded twice. This systematic relationship between paper and envelope sizes is one of the most practical aspects of the ISO standard — you never have to guess which envelope fits which paper.

Pixel Dimensions for Digital Design

When creating digital documents for print, knowing the pixel dimensions at your target resolution is essential. At 72 DPI (screen resolution), A4 is 595 × 842 pixels — used for web-optimized PDFs and screen previews. At 150 DPI (draft quality), A4 is 1240 × 1754 pixels — adequate for internal documents. At 300 DPI (print quality), A4 is 2480 × 3508 pixels — the professional standard for offset printing, brochures, and high-quality output. For large-format printing (posters, banners), even higher resolutions may be needed. Adobe Photoshop, Illustrator, InDesign, Canva, and Figma all use these pixel dimensions when setting up documents for print. This calculator provides instant reference for all three resolutions.

Practical Applications

Knowing paper sizes affects dozens of daily tasks. Printer settings must match the loaded paper — selecting A4 when US Letter is loaded wastes paper and creates misaligned prints. Photo printing uses specific sizes: 4×6 inches (10×15 cm), 5×7 (13×18 cm), 8×10 (20×25 cm). Business cards are typically 3.5×2 inches (89×51 mm) in the US or 85×55 mm in Europe. Posters come in standard sizes: A1 for academic posters, A2 for movie posters, B1 for bus shelter advertising. Shipping labels, sticky notes, index cards, and greeting cards all have standard dimensions. This calculator serves as a complete reference for anyone who works with paper in any capacity — from students printing homework to graphic designers preparing press-ready files.

Paper may seem old-fashioned in a digital age, but physical documents remain essential in business, education, law, government, and creative industries. This calculator ensures you always know the exact dimensions you need — whether ordering paper, setting up a document, choosing an envelope, or configuring a digital canvas for print.

From student homework to professional press sheets, from wedding invitations to architectural blueprints — paper sizes shape how we communicate in the physical world. This calculator is your complete reference for every standard dimension.