T-Bone steaks and Porterhouse steaks are the same. The Porterhouse is just a larger version of the T-Bone because it is carved from the larger portion of the tenderloin. A Porterhouse is the “King of the T-Bones”.
Both are cut from the short loin area of the beef. A center “T-Shaped Bone” divides two sides of the steak. On one side is a tenderloin filet and the other is a top loin which is better known as the New York Strip Steak.When the bone is removed, the result is two distinctly different steaks. A Filet and a New York Strip. When the bone is left on either side, it becomes either a “Bone-in Filet” or a “Bone-in New York Strip”.
Source: Differences Between Steaks