Prinz Adalbert and Friedrich Carl were armed with a main battery of four 21 cm (8.3 in) SK L/40 guns in two twin turrets, one on either end of the main superstructure.
The four guns were supplied with a total of 340 rounds of ammunition, or 85 shells per gun.
The turrets could depress to −5° and elevate to 30°, which provided a maximum range of 16,300 m (53,500 ft).
The 21 cm gun fired a 238-pound (108 kg) shell at a muzzle velocity of 780 m (2,560 ft) per second.
The ships' secondary armament consisted of ten 15 cm (5.9 in) SK L/40 guns, all placed in the sides of the hulls.
Three guns were mounted in casemates amidships on either side, with a pair of gun turrets above them.
These guns were provided with a total of 1,400 shells, or 140 per gun.
These guns fired an 40-kilogram (88 lb) projectile at a muzzle velocity of 800 m (2,600 ft) per second.
The guns could elevate to 30°, allowing a maximum range of 13,700 m (44,900 ft).

The ships also carried twelve 8.8 cm SK L/35 guns for close in defense; these were arranged in groups of four in shielded pivot mounts.
Four guns were mounted around the forward conning tower, four were located around the rear two funnels amidships, with the last four guns placed on top of the rear superstructure.
These guns fired a 7 kg (15 lb) shell at a muzzle velocity of 770 m (2,530 ft) per second.
They could elevate to 25° and could engage targets out to 9,090 m (29,820 ft).
The vessels' armament system was rounded out by four 45 cm (17.7 in) submerged torpedo tubes.
They were mounted in the bow, stern, and on each broadside, and supplied with eleven torpedoes.
Prinz Adalbert and Friedrich Carl were armed with a main battery of four 21 cm (8.3 in) SK L/40 guns in two twin turrets, one on either end of the main superstructure. The four guns were supplied with a total of 340 rounds of ammunition, or 85 shells per gun. The turrets could depress to −5° and elevate to 30°, which provided a maximum range of 16,300 m (53,500 ft). The 21 cm gun fired a 238-pound (108 kg) shell at a muzzle velocity of 780 m (2,560 ft) per second. The ships' secondary armament consisted of ten 15 cm (5.9 in) SK L/40 guns, all placed in the sides of the hulls. Three guns were mounted in casemates amidships on either side, with a pair of gun turrets above them. These guns were provided with a total of 1,400 shells, or 140 per gun. These guns fired an 40-kilogram (88 lb) projectile at a muzzle velocity of 800 m (2,600 ft) per second. The guns could elevate to 30°, allowing a maximum range of 13,700 m (44,900 ft).
The ships also carried twelve 8.8 cm SK L/35 guns for close in defense; these were arranged in groups of four in shielded pivot mounts. Four guns were mounted around the forward conning tower, four were located around the rear two funnels amidships, with the last four guns placed on top of the rear superstructure. These guns fired a 7 kg (15 lb) shell at a muzzle velocity of 770 m (2,530 ft) per second. They could elevate to 25° and could engage targets out to 9,090 m (29,820 ft). The vessels' armament system was rounded out by four 45 cm (17.7 in) submerged torpedo tubes. They were mounted in the bow, stern, and on each broadside, and supplied with eleven torpedoes.
Prinz Adalbert-class cruiser