Some people find it adequate to have enough supplies for a few weeks.
Others prefer several months. I know many people that have a year's supply of food and other necessities on hand. While a year's supply of provisions may seem a lot, I have to say that I've also known several families where the husband has lost his job, and the family was able to survive his period of unemployment because of their food storage and savings. It is up to you how prepared you want to be. Sometimes a family is forced to hurriedly evacuate their home, either for an act of nature or a toxic spill on a road nearby, for instance.