Screen size is measured diagonally. A laptop with a 17-inch screen will have a diagonal measurement of 17 inches, but the actual width of the screen will be smaller. For example the Apple 17-inch MacBook Pro has a diagonal screen measurement of 17 inches, but the actual width of the screen is 15.4 inches. If you're unsure about the size of your laptop and would like to know if it will fit in one of our bags, please feel free to contact us and we'll look up the dimensions for you.