Some later medieval castles had walls that were only about 15 to 20 feet (4.6 m to 6 m) high, but the walls of the stronger castles typically measured about 30 feet (9 m) in height and sometimes more.

The height of an average medieval castle varied significantly depending on its purpose and era, but standard defensive curtain walls typically stood between 30 and 40 feet (9 to 12 meters) tall. This height was specifically designed to be taller than the longest portable ladders used during a siege. The keep or main tower was significantly taller to provide a vantage point, often reaching 80 to 100 feet (24 to 30 meters). For instance, the White Tower at the Tower of London is approximately 90 feet high. Thicker walls at the base often tapered as they rose to maintain structural integrity. While fantasy media often depicts "sky-high" fortresses, real-world castles were limited by the physics of masonry and the immense cost of hauling stone. A wall higher than 50 feet was rare and usually only found in major royal fortifications like Coucy in France, which featured a massive donjon that once stood 180 feet tall before its destruction in World War I.