What Is A3 Card Size? Complete Guide

The A3 card size, also known as ISO 216 size “B”. This size is often used for posters, diagrams, and other types of large-scale documents and presentations. A3 paper is roughly twice the size of standard letter-size paper, making it ideal for creating large and detailed visuals.

The A3 card size measures 297 x 420 millimeters or 11.7 x 16.5 inches. It has an aspect ratio of 1:√2, which means that if you fold an A3 card in half, you get two A4-sized sheets. The A3 card size is double the size of an A4 sheet and half the size of an A2 sheet.

What Is an A3 Card?

A3 is a widely used paper size that is commonly used for various purposes, including printing, artwork, and graphic design. The A3 card size is specifically used for creating cards, posters, presentations, and other visual materials. Here are the dimensions and specifications of the A3 card size, as well as a comparison with other common paper sizes:

A3 Card Size

Dimensions and Specifications of A3 Card Size:

The A3 card size measures 297 x 420 millimeters or 11.7 x 16.5 inches. It has an aspect ratio of 1:√2, which means that if you fold an A3 card in half, you get two A4-sized sheets. The A3 card size is double the size of an A4 sheet and half the size of an A2 sheet.

Comparison with Other Common Paper Sizes:

A3: 297 x 420 mm (11.7 x 16.5 inches)
A4: 210 x 297 mm (8.3 x 11.7 inches)
A2: 420 x 594 mm (16.5 x 23.4 inches)
A1: 594 x 841 mm (23.4 x 33.1 inches)

The A3 card size is larger than A4 but smaller than A2 and A1. It is commonly used when you need a larger canvas than A4 but doesn’t require a very large format like A2 or A1. It strikes a balance between size and portability, making it suitable for various applications.

Weight and Thickness Considerations:

When it comes to weight and thickness, A3 card sizes can vary depending on the specific type of cardstock or paper used. The weight of the cardstock is typically measured in grams per square meter (gsm). Common weights for A3 cards range from 200 gsm to 300 gsm.

The thickness of the cardstock or paper is often measured in micrometers (µm) or points (pt). A typical A3 card may have a thickness between 250 µm and 350 µm or between 10 pt and 14 pt. However, these measurements can vary depending on the specific manufacturer and the intended use of the card.

Related: Standard Card Envelope Sizes And Dimensions

What Are The Uses of A3 Cards?

A3 cards are commonly used for a variety of professional and personal purposes. Some of the most common uses include:

  1. Posters and presentations: The large size of A3 cards makes them ideal for creating posters and presentations that need to be easily read from a distance.
  2. Diagrams and blueprints: Architects, engineers, and other professionals use A3 cards to create detailed diagrams and blueprints that need to be easily read by others.
  3. Photography and artwork: A3 cards are often used to print high-quality photos and artwork, as they provide a larger canvas than standard letter-size paper.
  4. Planning and organization: Some businesses and individuals use A3 cards to create visual plans and to organize information in a clear and easy-to-read format.
  5. Marketing and Advertising: A3 size cards are suitable for creating advertising posters, brochures, flyers, and so on.
  6. Education and Training: Teachers and trainers may use A3 size cards for creating diagrams, charts, mind maps, and infographics for the classroom and training session.

Envelope Sizes for A3 Cards

When mailing an A3 card, it is important to use an envelope that is the appropriate size to ensure that the card fits securely and arrives in good condition. The most common envelope size for an A3 card is C3.

A C3 envelope measures 458mm x 324mm (18.03 inches x 12.76 inches), which is slightly larger than an A3 sheet of paper, providing enough room for the card to fit comfortably without bending. The C3 envelope has a wide opening at the top, making it easy to insert and remove the card.

Another option for mailing A3 cards is to use a flat poly bag. It’s a protective bag that seals around the card and prevents damage from bending, moisture or dust. It will also make the card look more professional.

When mailing an A3 card, it is important to keep in mind that while the card and envelope may be the correct size, the package may still be too large to be considered a standard letter by some postal services. Therefore, it may require additional postage and may be subject to oversized mail fees. In this case, it is important to check with your local postal service for the specific guidelines and fees for mailing large format items such as A3 cards.

In general, It’s always a good idea to test the mailing option with a sample and weigh it before mailing a large amount of them to ensure it will reach the destination without any issues.

Related: Shutterfly Wallet Sizes


So in this post, I have discussed the dimensions of a3 card size, what it is used for and the best envelope sizes to use when mailing an A3 card. I have also discussed some tips on how to make sure that the card will safely reach its destination. I hope this post provides some useful information on A3 card size and their uses.


What size is an A3 card in MM?

The size of an A3 card is 297 x 420 millimeters (mm).

Is the A3 card bigger than A4?

Yes, the A3 card is bigger than A4. A4 measures 210 x 297 mm, while A3 measures 297 x 420 mm.

Is A3 a letter size?

No, A3 is not a letter size. Letter size paper is a common paper size in the United States and measures 8.5 x 11 inches, which is approximately 216 x 279 mm.

What size is an A2 card?

The size of an A2 card is 420 x 594 mm.

Leave a Comment