What size is A4 paper?

A4 measures 210 × 297 mm (8.27 × 11.69 inches).

What is the largest A-series size?

A0 is the largest at 841 × 1189 mm.

What is the smallest A-series size?

A10 is the smallest at 26 × 37 mm.

All A-series sizes maintain a √2 aspect ratio, so folding any A size in half gives the next size down.

A-Series Paper Sizes – Complete Guide 2026

A-Series Paper Sizes Explained

The A-series is the world's most widely used paper size standard, defined by ISO 216. Every size maintains a √2 (1:1.414) aspect ratio, meaning folding an A3 in half gives you an A4, folding A4 gives A5, and so on.

📊 A-Series Quick Facts:
• Largest: A0 (841 × 1189 mm)
• Most Used: A4 (210 × 297 mm)
• Smallest: A10 (26 × 37 mm)
• Aspect Ratio: 1:√2 for all sizes

📏 Complete A-Series Dimensions

Size	Millimetres	Inches	Convert
A0	841 × 1189 mm	33.1 × 46.8 in	→ Pixels
A1	594 × 841 mm	23.4 × 33.1 in	→ Pixels
A2	420 × 594 mm	16.5 × 23.4 in	→ Pixels
A3	297 × 420 mm	11.7 × 16.5 in	→ Pixels
A4	210 × 297 mm	8.3 × 11.7 in	→ Pixels
A5	148 × 210 mm	5.8 × 8.3 in	→ Pixels
A6	105 × 148 mm	4.1 × 5.8 in	→ Pixels
A7	74 × 105 mm	2.9 × 4.1 in	—
A8	52 × 74 mm	2.0 × 2.9 in	—
A9	37 × 52 mm	1.5 × 2.0 in	—
A10	26 × 37 mm	1.0 × 1.5 in	—