Card Stock Sizes

Misnomer for "A" sizes.

Normally, A3 is bigger than A4 or A6 bigger than A7. That is for The International Paper Standard (ISO 216). Smaller number = Bigger paper But there is another "A" naming from the North American "Announcement" Sizes. In this cases, A7 is bigger than A6 and so on. Larger number = Bigger card They are referring to entirely different sizing reference.

Common Size for Cards

A7 Size (5" x 7") — The Most Common. This is the standard and most popular size for both handmade and commercially produced pop-up cards. It provides a large enough "floor" (the inside base of the card) for intricate pop-up mechanisms—like a bouquet of flowers or a cityscape—to expand fully without sticking out of the edges when close

Square Sizes (5" x 5" or 6" x 6") — The Modern Favorite. Many premium 3D pop-up card brands (like Lovepop) use square dimensions. The perfect symmetry of a square card makes it incredibly easy to design center-fold pop-up mechanisms that open evenly in all directions (like a tiered birthday cake or a blooming lotus). Requires a square envelope (note that square envelopes often require extra postage if you are mailing them).

When designing a pop-up card, the most important rule of thumb regarding size is that the tallest part of your pop-up mechanism inside cannot be longer than the width or height of the closed card, otherwise, the paper will stick out of the edges when folded shut!

Common Confusion of Cards.

a super common point of confusion when making cards!

When we say a card is "15 cm x 15 cm", we are talking about the size of the card when it is folded shut (the size that goes into the envelope).

So, let's break down the exact measurements:

When Closed: The card is 15 cm wide and 15 cm tall.

When Open (Flat): You are exactly right—it is 30 cm in total length! If it opens like a book, the open paper will be 30 cm wide and 15 cm tall.