How do I know if a laptop will actually fit in a leather backpack?

Measure your laptop's screen diagonally, corner to corner, ignoring the frame, then round down to the nearest inch. If that number matches or is smaller than the size listed for the bag's laptop compartment, it'll fit. The Gloria backpack and the Dora and Tora satchels are all built around this sizing logic, which is why the XL and L versions tend to work best for larger 15 and 16-inch laptops.