German Type IXD2 submarines were considerably larger than the original Type IXs. The U-864 had a displacement of 1,610 tonnes (1,580 long tons) when at the surface and 1,799 tonnes (1,771 long tons) while submerged.[3] The U-boat had a total length of 87.58 m (287 ft 4 in), a pressure hull length of 68.50 m (224 ft 9 in), a beam of 7.50 m (24 ft 7 in), a height of 10.20 m (33 ft 6 in), and a draught of 5.35 m (17 ft 7 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines plus two MWM RS34.5S six-cylinder four-stroke diesel engines for cruising, producing a total of 9,000 metric horsepower (6,620 kW; 8,880 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged.