What Size Is A3 Paper? Simple Guide in Inches, cm, and mm

A3 paper is one of the most popular paper sizes used in offices, schools, and creative fields. It’s known for its versatility and balanced size, making it ideal for both everyday documents and large-format prints.

A3 paper measuring 297 x 420 millimeters (29.7 x 42 cm or 11.7 x 16.5 inches), A3 offers twice the space of A4 without being too bulky. This makes it perfect for projects that require extra room for visuals or detailed information.

Designers, educators, and professionals often choose A3 for posters, blueprints, and ledgers. Its clarity and scalability make it a reliable choice.

In this guide, we’ll explore what A3 paper size really means, its measurements, and how it’s used in different industries.

TL;DR

A3 paper size is 11.7 x 16.5 in (297 x 420 mm) double the size of A4. It’s perfect for posters, diagrams, blueprints, and large documents. Following the ISO 216 standard, A3 maintains a consistent aspect ratio for easy scaling, making it ideal for professional, educational, and creative printing needs.

Understanding A3 Paper Dimensions

A3 paper follows the ISO 216 standard used worldwide, especially in Europe and Asia. Its exact size is 297 millimeters by 420 millimeters, or 11.7 inches by 16.5 inches. The total area of an A3 sheet is 0.125 square meters (1250 cm²), which offers plenty of space for detailed layouts and large visual content.

Measurement System	Width	Height	Area
Millimeters (mm)	297 mm	420 mm	0.125 m²
Centimeters (cm)	29.7 cm	42 cm	1250 cm²
Inches (in)	11.7 in	16.5 in	0.14 yd²

A unique feature of A-series paper sizes is their proportional relationship. If you fold an A3 sheet in half along its shorter edge, you get two A4 sheets, each maintaining the same aspect ratio of 1:√2. This makes resizing documents between formats simple and efficient.

Common Uses for A3 Paper

A3 paper is incredibly versatile. It’s often used when standard A4 sheets are too small to capture all the details or design elements you need. Here are some of the most popular uses:

• Posters and promotional materials – Perfect for advertising, flyers, and visual displays.

• Diagrams and blueprints – Common in architecture, engineering, and construction drawings.

• Ledgers and spreadsheets – Used in business and accounting for large tables or reports.

• Flip charts and presentations – Ideal for meetings and classroom activities.

In creative and educational settings, A3 paper also works well for art projects, sketches, and storyboards, allowing ample space for creativity.

Why Choose A3 Paper?

Correct A3 Paper Size

A3 paper is a favorite because of its balance between size and practicality. It’s large enough to make visuals stand out but still fits into most standard printers and copiers that support wide-format printing. Designers and educators appreciate it for displaying information clearly without feeling cluttered.

Another benefit is that A3 paper is easy to scale. Since it follows the same aspect ratio as all A-series sizes, you can enlarge or reduce your design to A2, A4, or A5 without distortion. This makes it perfect for print layouts, graphic design, and multi-format projects.

Also read: What is The Size of A5 Paper

Paper Weight and Material Options

A3 paper comes in many thicknesses and finishes. The most common weights range from 80 gsm (grams per square meter) for everyday use to 200–300 gsm for premium prints or artwork.

Glossy, matte, and textured finishes are available depending on whether the goal is to print text-heavy documents or vivid, colorful posters.

Choosing the right paper weight can make a huge difference in quality - lighter paper is flexible and budget-friendly, while heavier stock offers durability and a premium feel.

A3 Paper in Everyday Use

While businesses often use A4 for letters and documents, A3 steps in when clarity and visibility matter most. For example, in classrooms, A3 posters make learning materials more engaging. In offices, engineers and architects rely on A3 blueprints to present detailed designs. Even at home, A3 paper can be used for art prints, calendars, or DIY projects.

Here’s a quick look at where you might find A3 paper:

• Marketing and design studios

• Schools and universities

• Construction and engineering firms

• Office presentation rooms

Its flexibility and standardization make it a must-have size across industries.

Tips for Printing on A3 Paper

When printing on A3, make sure your printer supports this paper size. Most standard office printers handle up to A4, while wide-format or multifunction printers can print on A3. Always check your printer settings to select the correct paper size before printing to ensure proper alignment and quality.

If you’re printing double-sided or borderless designs, using heavier paper (120gsm or above) helps prevent ink bleed and gives your prints a more professional look.

Also read: What is The Correct Legal Paper Size

How Big Is A3 Compared to A4?

To put it simply, A3 paper is twice the size of A4. This means that two A4 pages placed side by side (along their longer edges) perfectly form an A3 sheet. This scalability makes A3 an ideal choice for expanding documents that were originally created in A4 format.

Quick comparison:

• A3: 297 x 420 mm (11.7 x 16.5 in)

• A4: 210 x 297 mm (8.3 x 11.7 in)

So, when you need more space for visuals, tables, or text-heavy layouts, A3 offers that extra breathing room without changing proportions.

How A3 Compares to Other Paper Sizes

To understand how A3 fits into the paper size family, here’s a quick comparison with some other common formats:

Paper Size	Dimensions (mm)	Dimensions (inches)	Relationship
A5	148 x 210	5.8 x 8.3	Half of A4
A4	210 x 297	8.3 x 11.7	Half of A3
A3	297 x 420	11.7 x 16.5	Double of A4
A2	420 x 594	16.5 x 23.4	Double of A3

This system ensures that when paper is folded or cut, it maintains the same aspect ratio (1:√2). That ratio makes scaling simple - ideal for designers and printers who need consistent proportions.

Which Paper Is Best For Everyday Use?

• A3 (11.7 x 16.5 Inches)
• A4 (8.3 x 11.7 Inches)
• A5 (5.8 x 8.3 Inches)
• Legal (8.5 × 14 Inches)

Conclusion

In conclusion, A3 paper's original size is 297 x 420 millimeters, or 11.7 x 16.5 inches. It provides a balanced format that’s spacious yet practical for everyday use.

Its larger surface makes it perfect for posters, charts, and creative layouts without compromising clarity.

Whether for business, education, or design, A3 remains a versatile and dependable paper size worldwide.