Many consumers get confused when trying to measure a laptop to see if it will fit into a laptop backpack. That’s because laptops are generally categorized by their screen size, which is measured diagonally, such as a 15-inch or 17-inch laptop.  And while many makers of laptop backpacks also suggest which sizes of laptops will fit in their backpacks (by their screen size), if you want to be certain, you’ll want to measure or find the width and the depth of your laptop. Then, compare them with the specs of the size of the compartments in your laptop backpack. To be safe, you might consider adding a quarter-of-an-inch to the backpack’s measurements.