Why your cat purrs has been a very complicated questions scientists have been working on, some of the explanations we have so far are the following: Happiness Your cat purring is a sign that they are very happy and excited, sometimes curled up in your lap getting pets or rolling around in the sun. Your cats purring is a indicator that they are happy and enjoying themselves in that moment. Calm nerves When acts get stressed or nervous they may purr to help themselves calm down