3x4

The 3x4 index card dimensions fall between the popular 3x5 and smaller 2x3 sizes. Measuring 3 inches wide by 4 inches high, it provides 12 square inches of surface area. This offers moderately more writing space than the highly compact 2x3 size while maintaining good portability. The versatility of the 3x4 size has led to it being called the multi-purpose index card. Its balance of portability and room for text makes it popular for simple flashcards, recipes, short notes, and lightweight organization. The 3x4 dimensions began to arise in the late 19th century as catalog cards transitioned from smaller to larger sizes. Libraries found it handy for succinct cataloging needs. Today, students, teachers, cooks, and others appreciate the 3x4 when they require a bit more space than tiny 2x3 cards but don't need the larger capacity of 3x5 and bigger sizes. It's an efficient middle-ground index card.