This largely depends on what you plan to do inside Intramuros. For those only wishing to do sightseeing and take photos, 2 hours will be enough. But if you wish to go inside the forts, churches, and other buildings, you will spend longer time than that. Also, it is recommended to take some refreshments or go for an entire meal in one of its many restaurants and cafes inside, so spare a little more time — close to half a day — to fully enjoy Intramuros.