The dimensions of the Great Hall very much depended on the size of the castle, and these came in all sizes, of course. An early but typical example, now in ruins, is the Great Hall of Chepstow Castle in Wales, built between 1067 and 1090 CE, which measured 30 x 12 metres (100 x 40 ft).

The size of a Great Hall varied significantly depending on the status of the castle's lord, but it was always the largest and most impressive room in the fortress. In a major royal castle, a Great Hall could be truly massive; for example, Westminster Hall (the Great Hall of the Palace of Westminster) measures roughly 240 feet long and 67 feet wide. More typical baronial Great Halls usually ranged from 40 to 80 feet in length. These rooms were designed with high ceilings—often featuring impressive timber "hammer-beam" roofs—to accommodate large crowds, heat from central hearths, and the display of wealth. The hall served as a multi-purpose space for feasting, holding court, receiving guests, and even sleeping for lower-ranking servants. It was typically divided into the "High End," where the lord's family sat on a raised dais, and the "Low End" near the entrance and kitchens. The sheer volume of the space was a physical manifestation of power, intended to awe visitors with the owner's ability to host hundreds of people and provide a "Grand Scale" of hospitality and security within the stone walls.