3x5

The 3x5 index card is one of the most popular and widely used card sizes. Measuring 3 inches wide by 5 inches tall, it has a total surface area of 15 square inches. Also referred to as the professor's index card or library card, it offers ample room for notes, reminders, and studying while still being highly portable. The 3x5 size became popular in the late 19th century as an easy way for students and researchers to organize information alphabetically using a card catalog filing system. Today, these versatile cards continue to be used for flashcards, recipes, writing ideas, and any other need for a portable paper surface to jot down information. Their ability to fit easily in a pocket or small bag makes 3x5 cards a timeless tool for organization and note taking for students, teachers, office workers, writers, and anyone else needing to capture information on-the-go.