The "Powerful"-class cruiser was designed to counter the Russian armoured cruiser which had been designed as a long-range commerce raider. This required long range and high speed to catch the Russian ship. The ships displaced at normal load. They had an overall length of , a beam of and a draught of . The ships were powered by a pair of four-cylinder triple-expansion steam engines, each driving one propeller shaft, using steam provided by 48 Belleville boilers. The engines were designed to produce a total of using forced draught and gave a maximum speed of . "Terrible" reached a maximum speed of from during her sea trials. She carried enough coal to give her a range of at and her complement consisted of 894 officers and ratings.