Paper Size Converter

About This Tool

The Paper Size Converter is a comprehensive reference for paper dimensions, unit conversions, and weight calculations. It covers all ISO A series sizes (A0 through A10), the B series (B0 through B10), US standard sizes (Letter, Legal, Tabloid, Executive), and allows custom dimension entry. Every size can be displayed in millimeters, centimeters, or inches, and the tool includes a GSM-to-pounds weight converter for both bond and text paper grades.

The ISO 216 Standard

The international paper size system is based on the ISO 216 standard, originally a German DIN standard from 1922. The system is built on a simple but brilliant mathematical property: the aspect ratio of every sheet is 1:sqrt(2), approximately 1:1.414. This is the only ratio where folding a sheet in half along the longer side produces a sheet with the same proportions. A0 paper has an area of exactly one square meter. A1 is half of A0, A2 is half of A1, and so on. This self-similar property makes it trivially easy to scale documents between sizes without cropping or distortion.

US Paper Sizes

The United States, Canada, and Mexico use a different paper size system based on imperial measurements. US Letter (8.5 x 11 inches) is the standard for office documents, while Legal (8.5 x 14 inches) is used for legal documents and contracts. Tabloid (11 x 17 inches) is used for newspapers, large spreadsheets, and architectural drawings. Unlike the ISO system, US sizes do not follow a consistent mathematical relationship between sizes, which makes scaling between them less straightforward.

B Series and Envelope Sizes

The B series provides intermediate sizes between A sizes. B sizes are the geometric mean between consecutive A sizes — B1 is between A0 and A1, B2 is between A1 and A2, and so forth. B sizes are primarily used for envelopes (the C series, which is closely related to B, defines envelope sizes specifically), posters, and books. B5 (176 x 250 mm) is a popular book format in Japan and many European countries, sitting comfortably between the too-small A5 and the too-large A4.

Understanding Paper Weight: GSM vs Pounds

Paper weight is expressed differently around the world. Most countries use GSM (grams per square meter), which is simple and unambiguous — it measures the mass of a single square meter of the paper. The US uses pounds (lbs), but with a critical complication: the basis weight depends on the paper category. Bond paper (used in offices) uses a basis size of 17 x 22 inches, while text paper (used in commercial printing) uses 25 x 38 inches. This means the same physical sheet of paper can be described as "20 lb bond" or "50 lb text" — same paper, different numbers. GSM eliminates this confusion entirely, which is why it is the preferred international standard.

Choosing the Right Paper Weight

For standard office printing and copying, 75-80 GSM is the norm. Professional letterhead and resumes look better on 90-120 GSM. Marketing brochures and flyers typically use 130-170 GSM for a substantial feel without being rigid. Greeting cards and postcards use 250-350 GSM. Business cards are usually 300-400 GSM for a sturdy, professional impression. When ordering from a print shop, always specify GSM to avoid ambiguity. If you are printing double-sided, choose a higher GSM (at least 100) to prevent show-through from the other side.

Practical Tips for Designers and Print Professionals

When preparing files for print, always set your document size to match the target paper size exactly, then add bleed (typically 3mm on all sides for commercial printing). Remember that printers have non-printable margins, so your safe area is about 5-10mm smaller than the paper size on each edge. For documents that may be printed on both A4 and Letter, design for the smaller common area (approximately 8.27 x 11 inches) with generous margins. When converting between paper sizes, the ISO system's consistent aspect ratio means you can scale any A-size document to any other A-size without layout changes — a significant advantage over US sizes.

Environmental Considerations

Paper weight directly affects shipping costs and environmental impact. A ream (500 sheets) of 80 GSM A4 paper weighs about 2.5 kg (5.5 lbs). Switching from 80 GSM to 75 GSM saves approximately 6% in paper weight and cost. For high-volume printing environments, this adds up significantly. Recycled paper is available in all standard sizes and weights, and modern recycled paper is nearly indistinguishable from virgin paper in quality. When possible, choose FSC-certified or recycled paper to reduce environmental impact without sacrificing print quality.