A Quick Guide to Paper Sizes

When shopping for notebooks, loose-leaf paper, or planners, you’ve probably noticed labels like A4, A5, B5, or Letter. But what do these sizes actually mean? Here’s a quick breakdown to help you pick the right one for your needs.

The A-Series (Most Common)

The A-series is the international standard (ISO 216) and the most widely used in Asia and Europe.

• A4 (210 × 297 mm / 8.3 × 11.7 in): The everyday workhorse. Standard printer paper size. Great for school and office use.
• A5 (148 × 210 mm / 5.8 × 8.3 in): Half of A4. Perfect for journals, planners, and portable notebooks.
• A6 (105 × 148 mm / 4.1 × 5.8 in): Small and pocket-friendly. Often used for memo pads or travel notebooks.

The B-Series

The B-series is slightly larger than A-series sizes, often used in Japan and for design/creative work.

• B5 (176 × 250 mm / 6.9 × 9.8 in): Popular for study notebooks (like Kokuyo) — big enough for notes, yet portable.

US Sizes

If you’re in the U.S., you’ll also encounter Letter size (8.5 × 11 in), which is close to A4 but not the same.

Which Should You Choose?

• A4/Letter: Best for printing and office documents.
• A5: Ideal for journaling and planners.
• B5: A sweet spot for students — roomy but still backpack-friendly.
• A6: Great for jotting down quick notes on the go.