You might wonder why not just wear a backpack to begin with. The problem is, it is quite difficult to find pretty backpacks with all the features (such as proper zipper, hidden pockets, many compartments, laptop sleeve) handbags often come with. Also, there are situations where you need to carry the bag over a long distance where no one really looks at you, followed by a period of time where either you need to have better control over your bag (such as a shopping center or public transport because of picpockets), or you simply need to look a bit more elegant and wear a handbag, which is a little harder to achieve with backpacks.
From time to time, convertible handbags/backpacks designed so that they look their best in both forms pop up, but they are still quite a rare occurence. So meanwhile, here is a tutorial on how to turn one type of handbags into a decent backpack in a super fast and simple way.
For this trick to work, the handbag must have a short handle as well as rings to attach cross-body strap. I know it sounds very specific, but most bigger handbags come in this design anyway. Then of course you need a detachable cross-body strap, but that one can come from another handbag as well.
Obviously, some designs look better as backpacks than others, but I think in most cases, you will still look better than if you wear a sports backpack or a completely non-matching backpack, even if the design is more elegant or cute.
It's really simple. Just attach one side of the cross-body strap to the ring on one side, thread the strap through the handles, and attach on the other side. It takes a bit of practice to put it on your back properly, but the basic design you need (i.e., loops for two hands) is there. Also, when you decide to wear the handbag as a handbag again, having the strap like this prevents it from dangling too low.