What is the difference between A4 and Letter size paper?

A4 measures 210×297mm (8.3"×11.7") and is the international standard, while Letter measures 216×279mm (8.5"×11") and is the North American standard. Letter is slightly wider but shorter than A4. A4 has an area of 0.062 m² while Letter has 0.060 m². When printing A4 documents on Letter paper, you may need to adjust margins or scaling.

How does the ISO A series paper sizing system work?

The ISO A series is based on a √2:1 aspect ratio, starting with A0 which has an area of exactly 1 square meter. Each subsequent size (A1, A2, A3, etc.) is created by folding the previous size in half, making it exactly half the area. This system allows perfect scaling - a document designed for A4 can be enlarged to A3 or reduced to A5 without distortion.

What are C series paper sizes used for?

C series sizes are defined by ISO 269 and are specifically designed for envelopes. Each C size is slightly larger than the corresponding A size to allow the A size paper to fit comfortably. For example, C4 envelopes (229×324mm) are designed to hold unfolded A4 paper (210×297mm), C5 for A5, and C6 for A6. This creates a perfect envelope system for the A series.

Why is Legal size paper 14 inches tall?

Legal size paper (8.5"×14") is 3 inches taller than Letter size to accommodate legal documents, contracts, and court filings that traditionally required more space for signatures, seals, and additional clauses. The extra length provides room for legal formatting requirements while maintaining the same width as Letter for compatibility with standard filing systems.

Can I print A3 documents on Letter or Legal size paper?

A3 (297×420mm or 11.7"×16.5") is larger than both Letter (8.5"×11") and Legal (8.5"×14") paper. To print A3 on these sizes, you would need to scale down the document significantly (to about 50-60%) or print it across multiple pages using tiling. Alternatively, use Tabloid/Ledger size (11"×17") which is closer to A3 dimensions.

What is the best paper size for posters and presentations?

For posters, A2 (420×594mm or 16.5"×23.4") and A1 (594×841mm or 23.4"×33.1") are popular choices for medium to large displays. A0 (841×1189mm or 33.1"×46.8") is ideal for large format posters. In North America, Tabloid (11"×17") works well for small posters, while larger custom sizes are often used. The choice depends on viewing distance and display location.

Paper Size Converter

Compare and convert between ISO A/B/C series and North American paper sizes with dimensions in mm and inches

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size

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Quick Presets

Common paper sizes for quick lookup

Input & Settings

Select paper size and DPI for pixel dimension calculation

Paper Size

Select a paper size and DPI to get dimensions in millimeters, inches, and pixels. Use 300 DPI for professional printing, 72 DPI for web.

DPI Quick Reference

Common DPI settings and their uses

72 DPI

Web graphics, screen display, email attachments

96 DPI

Windows standard, web images, digital presentations

150 DPI

Draft printing, newspaper quality, quick prints

300 DPI

Professional printing, magazines, high-quality photos

📐 Paper Size Standards

• ISO A Series: International standard, each size is half the area of the previous
• ISO B Series: Intermediate sizes between A series
• ISO C Series: Envelope sizes designed to fit A series paper
• US Sizes: Letter, Legal, and Tabloid are North American standards
• Pixel Calculation: Pixels = (mm ÷ 25.4) × DPI

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