The design of the St Vincent class was derived from that of the previous Bellerophon class, with a slight increase in size, armour and more powerful guns, among other minor changes.
Vanguard had an overall length of 536 feet (163.4 m), a beam of 84 feet (25.6 m), and a normal draught of 28 feet (8.5 m).
She displaced 19,700 long tons (20,000 t) at normal load and 22,800 long tons (23,200 t) at deep load.
In 1910 her crew numbered 753 officers and ratings.

Vanguard was powered by two sets of Parsons direct-drive steam turbines, each driving two shafts, using steam from eighteen Babcock & Wilcox boilers.
The turbines were rated at 24,500 shaft horsepower (18,300 kW) and intended to give the ship a maximum speed of 21 knots (39 km/h; 24 mph).
During her sea trials on 17 December 1909, she unofficially reached a top speed of 22.3 knots (41.3 km/h; 25.7 mph) from 25,780 shp (19,220 kW), although she must have been lightly loaded to reach this speed.
Vanguard carried enough coal and fuel oil to give her a range of 6,900 nautical miles (12,800 km; 7,900 mi) at a cruising speed of 10 knots (19 km/h; 12 mph).

The St Vincent class was equipped with ten breech-loading (BL) 12-inch (305 mm) Mk XI guns in five twin-gun turrets, three along the centreline and the remaining two as wing turrets.
The centreline turrets were designated 'A', 'X' and 'Y', from front to rear, and the port and starboard wing turrets were 'P' and 'Q' respectively.
The secondary, or anti-torpedo boat armament, comprised twenty BL 4-inch (102 mm) Mk VII guns.
Two of these guns were each installed on the roofs of the fore and aft centreline turrets and the wing turrets in unshielded mounts, and the other ten were positioned in the superstructure.
All guns were in single mounts.
The ships were also fitted with three 18-inch (450 mm) torpedo tubes, one on each broadside and the third in the stern.

The St Vincent-class ships were protected by a waterline armoured belt 8–10 inches (203–254 mm) thick that extended between the end barbettes.
Their decks ranged in thickness between 0.75 to 3 inches (19 to 76 mm) with the thickest portions protecting the steering gear in the stern.
The main battery turret faces were 11 inches (279 mm) thick, and the turrets were supported by barbettes 9–10 inches (229–254 mm) thick.
The design of the St Vincent class was derived from that of the previous Bellerophon class, with a slight increase in size, armour and more powerful guns, among other minor changes. Vanguard had an overall length of 536 feet (163.4 m), a beam of 84 feet (25.6 m), and a normal draught of 28 feet (8.5 m). She displaced 19,700 long tons (20,000 t) at normal load and 22,800 long tons (23,200 t) at deep load. In 1910 her crew numbered 753 officers and ratings.
Vanguard was powered by two sets of Parsons direct-drive steam turbines, each driving two shafts, using steam from eighteen Babcock & Wilcox boilers. The turbines were rated at 24,500 shaft horsepower (18,300 kW) and intended to give the ship a maximum speed of 21 knots (39 km/h; 24 mph). During her sea trials on 17 December 1909, she unofficially reached a top speed of 22.3 knots (41.3 km/h; 25.7 mph) from 25,780 shp (19,220 kW), although she must have been lightly loaded to reach this speed. Vanguard carried enough coal and fuel oil to give her a range of 6,900 nautical miles (12,800 km; 7,900 mi) at a cruising speed of 10 knots (19 km/h; 12 mph).
The St Vincent class was equipped with ten breech-loading (BL) 12-inch (305 mm) Mk XI guns in five twin-gun turrets, three along the centreline and the remaining two as wing turrets. The centreline turrets were designated 'A', 'X' and 'Y', from front to rear, and the port and starboard wing turrets were 'P' and 'Q' respectively. The secondary, or anti-torpedo boat armament, comprised twenty BL 4-inch (102 mm) Mk VII guns. Two of these guns were each installed on the roofs of the fore and aft centreline turrets and the wing turrets in unshielded mounts, and the other ten were positioned in the superstructure. All guns were in single mounts. The ships were also fitted with three 18-inch (450 mm) torpedo tubes, one on each broadside and the third in the stern.
The St Vincent-class ships were protected by a waterline armoured belt 8–10 inches (203–254 mm) thick that extended between the end barbettes. Their decks ranged in thickness between 0.75 to 3 inches (19 to 76 mm) with the thickest portions protecting the steering gear in the stern. The main battery turret faces were 11 inches (279 mm) thick, and the turrets were supported by barbettes 9–10 inches (229–254 mm) thick.
HMS Vanguard (1909)