What are standard paper sizes?

Standard paper sizes are internationally agreed-upon dimensions for sheets of paper, designed to simplify printing, mailing, and document handling. The most widely used system is the ISO 216 standard, which defines the A, B, and C series. Each series follows a consistent aspect ratio of 1:√2, meaning that folding a sheet in half along its longer side produces two sheets of the next smaller size with the same proportions. This elegant mathematical property makes scaling between sizes seamless — an A3 sheet folded in half becomes an A4.

The A series is designed for general printing and office use, with A4 (210 × 297 mm) being the most common worldwide. The B series provides intermediate sizes between consecutive A sizes, often used for posters and books. The C series defines envelope sizes, where each C size is designed to fit the corresponding A size sheet. In North America, a separate system based on inches is used, with Letter (8.5 × 11 in) and Legal (8.5 × 14 in) being the most common formats.

Understanding paper dimensions in different units — millimeters, centimeters, inches, pixels, or points — is essential for designers, printers, and developers who need to prepare artwork, configure print settings, or create digital documents at the correct resolution.

Tool description

This tool instantly calculates the dimensions of any standard paper size across ISO A, B, C series and US formats. Select a paper series and specific size, choose your preferred unit of measurement, and get precise width, height, area, diagonal, and aspect ratio values. A complete reference table for all sizes in the selected series is also displayed, making it easy to compare dimensions at a glance.

Examples

Paper Size Width × Height (mm) Width × Height (in) Width × Height (px @ 300 DPI)
A4 210 × 297 8.27 × 11.69 2480 × 3508

Features

  • Multiple paper series: ISO A (A0–A10), ISO B (B0–B10), ISO C (C0–C10), and US sizes (Letter, Legal, Tabloid, Ledger, and more)
  • Five unit options: Millimeters, centimeters, inches, pixels, and typographic points
  • Custom DPI setting: Adjust DPI for accurate pixel and point calculations, essential for print-ready and screen designs
  • Complete metrics: Width, height, area, diagonal length, and aspect ratio for every selected size
  • Quick reference table: View all sizes in the selected series at once with clickable rows for instant selection

Use cases

  • Graphic designers preparing print-ready artwork who need exact pixel dimensions at a specific DPI for tools like Photoshop or Figma
  • Office professionals comparing paper sizes when setting up documents, choosing envelopes (C series), or configuring printer settings
  • Web developers building print stylesheets or PDF generators who need paper dimensions in CSS points or pixels

Supported sizes

ISO A Series: A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10

ISO B Series: B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10

ISO C Series (Envelopes): C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10

US Sizes: Letter, Legal, Tabloid, Ledger, Junior Legal, Half Letter, Government Letter

How it works

All paper sizes are stored in millimeters as their base unit. When you select a different unit, the tool converts dimensions using standard conversion factors:

  • Centimeters: mm ÷ 10
  • Inches: mm ÷ 25.4
  • Pixels: (mm ÷ 25.4) × DPI
  • Points: (mm ÷ 25.4) × 72

The area is calculated as width × height in the selected unit, the diagonal uses the Pythagorean theorem, and the aspect ratio is derived by dividing both dimensions by their greatest common divisor.

FAQ

Why is DPI only available for pixels and points? DPI (dots per inch) only affects resolution-dependent units. Millimeters, centimeters, and inches are physical measurements that don't change with resolution.

What DPI should I use? For print, 300 DPI is standard. For web or screen display, 72 or 96 DPI is typical. For high-quality photo printing, 600 DPI may be used.

What's the difference between the B and C series? The B series provides sizes between consecutive A sizes and is used for books, posters, and passports. The C series defines envelope dimensions — each C size is designed to hold the corresponding A size paper.