Kasuga had an overall length of 111.73 meters (366 ft 7 in), a beam of 18.71 meters (61 ft 5 in), a molded depth of 12.1 meters (39 ft 8 in) and a deep draft (ship) of 7.31 meters (24 ft 0 in).
She displaced 7,700 metric tons (7,600 long tons) at normal load.
The ship was powered by two vertical triple-expansion steam engines, each driving one shaft, using steam from 8 coal-fired Scotch marine boilers.
Designed for a maximum output of 13,500 indicated horsepower (10,100 kW) and a speed of 20 knots (37 km/h; 23 mph), Kasuga barely exceeded this, reaching a speed of 20.05 knots (37.13 km/h; 23.07 mph) during her sea trials on 20 September 1903 despite 14,944 ihp (11,144 kW) produced by her engines.
She had a cruising range of 5,500 nautical miles (10,200 km; 6,300 mi) at 10 knots (19 km/h; 12 mph).
Her complement consisted of 560 officers and enlisted men.

Her main armament consisted of one 40-caliber Armstrong Whitworth 10-inch/40 Type 41 gun in a single turret forward and two 8-inch/45 Type 41 guns, in a twin-gun turret aft.
Ten of the quick-firing (QF) 6-inch/40 Type 41 guns that comprised her secondary armament were arranged in casemates amidships on the main deck; the remaining four guns were mounted on the upper deck.
Kasuga also had ten QF 3-inch/40 Type 41 guns and six QF 3-pounder Hotchkiss guns to defend herself against torpedo boats.
She was fitted with four submerged 457 mm (18.0 in) torpedo tubes, two on each side.

In 1924 two of her 3 in/40 guns were removed, as were all of her QF 3-pounder Hotchkiss guns, and a single 8 cm/40 3rd Year Type anti-aircraft gun was added.
By August 1933, all ten of her casemated 6-inch guns had been removed in addition to four more 3 in/40 guns.

The ship's waterline armor belt had a maximum thickness of 150 millimeters (5.9 in) amidships and tapered to 70 millimeters (2.8 in) towards the ends of the ship.
Between the main gun barbettes it covered the entire side of the ship up to the level of the upper deck.
The ends of the central armored citadel were enclosed by transverse bulkheads 120 millimeters (4.7 in) thick.
The forward barbette, the conning tower, and gun turrets were also protected by 150-millimeter armor while the aft barbette only had 100 millimeters (3.9 in) of armor.
Her deck armor ranged from 20 to 40 millimeters (0.8 to 1.6 in) thick and the 6-inch guns on the upper deck were protected by gun shields.
Kasuga had an overall length of 111.73 meters (366 ft 7 in), a beam of 18.71 meters (61 ft 5 in), a molded depth of 12.1 meters (39 ft 8 in) and a deep draft (ship) of 7.31 meters (24 ft 0 in). She displaced 7,700 metric tons (7,600 long tons) at normal load. The ship was powered by two vertical triple-expansion steam engines, each driving one shaft, using steam from 8 coal-fired Scotch marine boilers. Designed for a maximum output of 13,500 indicated horsepower (10,100 kW) and a speed of 20 knots (37 km/h; 23 mph), Kasuga barely exceeded this, reaching a speed of 20.05 knots (37.13 km/h; 23.07 mph) during her sea trials on 20 September 1903 despite 14,944 ihp (11,144 kW) produced by her engines. She had a cruising range of 5,500 nautical miles (10,200 km; 6,300 mi) at 10 knots (19 km/h; 12 mph). Her complement consisted of 560 officers and enlisted men.
Her main armament consisted of one 40-caliber Armstrong Whitworth 10-inch/40 Type 41 gun in a single turret forward and two 8-inch/45 Type 41 guns, in a twin-gun turret aft. Ten of the quick-firing (QF) 6-inch/40 Type 41 guns that comprised her secondary armament were arranged in casemates amidships on the main deck; the remaining four guns were mounted on the upper deck. Kasuga also had ten QF 3-inch/40 Type 41 guns and six QF 3-pounder Hotchkiss guns to defend herself against torpedo boats. She was fitted with four submerged 457 mm (18.0 in) torpedo tubes, two on each side.
In 1924 two of her 3 in/40 guns were removed, as were all of her QF 3-pounder Hotchkiss guns, and a single 8 cm/40 3rd Year Type anti-aircraft gun was added. By August 1933, all ten of her casemated 6-inch guns had been removed in addition to four more 3 in/40 guns.
The ship's waterline armor belt had a maximum thickness of 150 millimeters (5.9 in) amidships and tapered to 70 millimeters (2.8 in) towards the ends of the ship. Between the main gun barbettes it covered the entire side of the ship up to the level of the upper deck. The ends of the central armored citadel were enclosed by transverse bulkheads 120 millimeters (4.7 in) thick. The forward barbette, the conning tower, and gun turrets were also protected by 150-millimeter armor while the aft barbette only had 100 millimeters (3.9 in) of armor. Her deck armor ranged from 20 to 40 millimeters (0.8 to 1.6 in) thick and the 6-inch guns on the upper deck were protected by gun shields.
Japanese cruiser Kasuga