Convert A0 to A5

📜 Origins

The A-series standard was invented in Germany in 1922 by engineer Walter Porstmann based on mathematical principles.

⚡ Historical Highlight

The US is one of the few countries still using Letter size. The rest of the world standardized on ISO 216 (A4) in 1975.

🎯 Fun Facts

• •A-series paper sizes (A4, A3, etc.) have a magical property: when folded in half, they maintain the same aspect ratio!
• •The aspect ratio of A-series paper is √2:1 (approximately 1.414:1) - discovered by mathematician Lichtenberg in 1786.
• •If you fold a piece of A4 paper 42 times (physically impossible), it would reach the moon.

🏛️ Archaeological Discovery

The oldest surviving paper is from 179-141 BCE in China, made from hemp. Papyrus from Egypt dates to 2400 BCE!

🚀 Modern Applications

A4 paper (210×297mm) is used by 95% of the world. US Letter (8.5×11") remains stubbornly American.