What are the dimensions of A4 paper?

A4 paper measures 210mm × 297mm (8.27 × 11.69 inches). It's the most commonly used paper size internationally for documents and printing, based on the ISO 216 standard.

How do paper sizes scale between A series?

Each A series paper size is exactly half the area of the previous size. For example, A4 is half of A3, and A5 is half of A4. The scaling factor between consecutive sizes is approximately 141.4% (or 70.7% when reducing).

What's the difference between A, B, and C series paper?

A series is the standard paper size for documents. B series is larger, used for posters and oversized prints (between consecutive A sizes). C series is designed for envelopes to fit A series paper - for example, a C4 envelope fits an unfolded A4 sheet.

How does US Letter size compare to A4?

US Letter (8.5 × 11 inches or 216 × 279mm) is slightly wider but shorter than A4 (210 × 297mm). A4 has a larger total area (62,370 mm²) compared to Letter (60,264 mm²).

What is the scaling percentage from A4 to A3?

To enlarge from A4 to A3, you need to scale by 141.4% (or √2). To reduce from A3 to A4, you scale by 70.7% (or 1/√2). This maintains the aspect ratio perfectly.

Paper Size Calculator - Convert & Compare ISO A, B, C & US Paper Sizes

About This Tool

This comprehensive paper size calculator helps you work with international and US paper standards. View dimensions in metric or imperial units, compare different paper sizes, calculate scaling ratios for printing and design work, and visualize size relationships. Perfect for graphic designers, print professionals, and anyone working with paper formats.

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📊 Quick Reference: All Paper Sizes

Size	Width	Height	Area	Common Use

💡 Pro Tips

A Series: Each size is exactly half the area of the previous one (e.g., A4 is half of A3)
Aspect Ratio: All ISO A, B, and C series maintain a √2:1 ratio (approximately 1.414:1)
Scaling: To enlarge A4 to A3, scale by 141.4%. To reduce, scale by 70.7%
Envelopes: C series envelopes are designed to fit unfolded A series paper (C4 fits A4)
US vs ISO: US Letter is slightly wider but shorter than A4
Printing: Use the scaling calculator to find exact percentages for your printer settings

📐 Paper Size Calculator

About This Tool

🎨 Custom Paper Size Calculator

📊 Quick Reference: All Paper Sizes

💡 Pro Tips