What is a good size apartment? Finding the Right Size Apartment. A studio can be between 350 and 600 square feet, a 1-bedroom is usually between 550 and 1,000 square feet, a 2-bedroom is around 1,000 square feet or more, and a one-bedroom of 3 approximately 1,200 square feet and up. How big is a 400 square meter apartment? Four hundred square feet is about the size of a two-car garage....