The design of Mikasa was a modified version of the Formidable-class battleships of the Royal Navy with two additional 6-inch (152 mm) guns.
Mikasa had an overall length of 432 feet (131.7 m), a beam of 76 feet (23.2 m), and a normal draught of 27 feet 2 inches (8.3 m).
She displaced 15,140 long tons (15,380 t) at normal load.
The crew numbered about 830 officers and enlisted men.

The ship was powered by two vertical triple-expansion steam engines, each driving one propeller, using steam generated by 25 Belleville boilers.
The engines were rated at 15,000 indicated horsepower (11,000 kW), using forced draught, and designed to reach a top speed of 18 knots (33 km/h; 21 mph) although Mikasa proved to be faster during her sea trials in December 1901, reaching 18.45 knots (34.17 km/h; 21.23 mph) from 16,341 indicated horsepower (12,185 kW).
She carried a maximum of 2,000 tonnes (2,000 long tons) of coal which allowed her to steam for 9,000 nautical miles (17,000 km; 10,000 mi) at a speed of 10 knots (19 km/h; 12 mph).

Mikasa's main battery consisted of the same four Elswick Ordnance Company 40-calibre twelve-inch guns used in all of the preceding Japanese battleships.
They were mounted in twin-gun barbettes fore and aft of the superstructure that had armoured hoods to protect the guns and were usually called gun turrets.
The hydraulically powered mountings could be loaded at all angles of traverse while the guns were loaded at a fixed angle of +13.5°.
They fired 850-pound (386 kg) projectiles at a muzzle velocity of 2,400 ft/s (730 m/s).

The ship's secondary armament consisted of fourteen 40-calibre 6-inch (152 mm) quick-firing guns mounted in casemates.
Ten of these guns were positioned on the main deck and the other four guns were placed above them at the corners of the superstructure.
They fired 100-pound (45 kg) shells at a muzzle velocity of 2,300 ft/s (700 m/s).
Protection against torpedo boat attacks was provided by twenty QF 12-pounder 12 cwt guns.
The 12-pounders fired 3-inch (76 mm), 12.5-pound (5.7 kg) projectiles at a muzzle velocity of 2,359 ft/s (719 m/s).
Lighter guns consisted of eight 47-millimetre (1.9 in) three-pounder Hotchkiss guns and eight 47-millimetre 2.5-pounder Hotchkiss guns.
The three-pounder gun fired 3.19-pound (1.45 kg) projectiles at a muzzle velocity of 1,927 ft/s (587 m/s) while the 2.5-pounder fired 2.5-pound (1.1 kg) shells at a muzzle velocity of 1,420 ft/s (430 m/s).
The ship was also equipped with four submerged 18-inch torpedo tubes, two on each broadside.

The waterline armour belt of Mikasa consisted of Krupp cemented armour that had a maximum thickness of 9 inches (229 mm) over the middle of the ship.
It was only 4 inches (102 mm) thick at the ends of the ship and was surmounted by a six-inch strake of armour that ran between the barbettes.
The barbettes were 14 inches (356 mm) thick, but reduced to six inches at the level of the lower deck.
The armour of the barbette hoods had a thickness of 8–10 inches (203–254 mm).
The casemates protecting the secondary armament were 2–6 inches (51–152 mm) thick and the deck armour was 2–3 inches (51–76 mm) in thickness.
The forward conning tower was protected by 14 inches of armour, but the aft conning tower only had four inches of armour.

Mikasa, like all the other Japanese battleships of the time, was fitted with four Barr & Stroud FA3 coincidence rangefinders that had an effective range of 7,300 metres (8,000 yd).
In addition the ships were also fitted with 24-power magnification telescopic gunsights.
The design of Mikasa was a modified version of the Formidable-class battleships of the Royal Navy with two additional 6-inch (152 mm) guns. Mikasa had an overall length of 432 feet (131.7 m), a beam of 76 feet (23.2 m), and a normal draught of 27 feet 2 inches (8.3 m). She displaced 15,140 long tons (15,380 t) at normal load. The crew numbered about 830 officers and enlisted men.
The ship was powered by two vertical triple-expansion steam engines, each driving one propeller, using steam generated by 25 Belleville boilers. The engines were rated at 15,000 indicated horsepower (11,000 kW), using forced draught, and designed to reach a top speed of 18 knots (33 km/h; 21 mph) although Mikasa proved to be faster during her sea trials in December 1901, reaching 18.45 knots (34.17 km/h; 21.23 mph) from 16,341 indicated horsepower (12,185 kW). She carried a maximum of 2,000 tonnes (2,000 long tons) of coal which allowed her to steam for 9,000 nautical miles (17,000 km; 10,000 mi) at a speed of 10 knots (19 km/h; 12 mph).
Mikasa's main battery consisted of the same four Elswick Ordnance Company 40-calibre twelve-inch guns used in all of the preceding Japanese battleships. They were mounted in twin-gun barbettes fore and aft of the superstructure that had armoured hoods to protect the guns and were usually called gun turrets. The hydraulically powered mountings could be loaded at all angles of traverse while the guns were loaded at a fixed angle of +13.5°. They fired 850-pound (386 kg) projectiles at a muzzle velocity of 2,400 ft/s (730 m/s).
The ship's secondary armament consisted of fourteen 40-calibre 6-inch (152 mm) quick-firing guns mounted in casemates. Ten of these guns were positioned on the main deck and the other four guns were placed above them at the corners of the superstructure. They fired 100-pound (45 kg) shells at a muzzle velocity of 2,300 ft/s (700 m/s). Protection against torpedo boat attacks was provided by twenty QF 12-pounder 12 cwt guns. The 12-pounders fired 3-inch (76 mm), 12.5-pound (5.7 kg) projectiles at a muzzle velocity of 2,359 ft/s (719 m/s). Lighter guns consisted of eight 47-millimetre (1.9 in) three-pounder Hotchkiss guns and eight 47-millimetre 2.5-pounder Hotchkiss guns. The three-pounder gun fired 3.19-pound (1.45 kg) projectiles at a muzzle velocity of 1,927 ft/s (587 m/s) while the 2.5-pounder fired 2.5-pound (1.1 kg) shells at a muzzle velocity of 1,420 ft/s (430 m/s). The ship was also equipped with four submerged 18-inch torpedo tubes, two on each broadside.
The waterline armour belt of Mikasa consisted of Krupp cemented armour that had a maximum thickness of 9 inches (229 mm) over the middle of the ship. It was only 4 inches (102 mm) thick at the ends of the ship and was surmounted by a six-inch strake of armour that ran between the barbettes. The barbettes were 14 inches (356 mm) thick, but reduced to six inches at the level of the lower deck. The armour of the barbette hoods had a thickness of 8–10 inches (203–254 mm). The casemates protecting the secondary armament were 2–6 inches (51–152 mm) thick and the deck armour was 2–3 inches (51–76 mm) in thickness. The forward conning tower was protected by 14 inches of armour, but the aft conning tower only had four inches of armour.
Mikasa, like all the other Japanese battleships of the time, was fitted with four Barr & Stroud FA3 coincidence rangefinders that had an effective range of 7,300 metres (8,000 yd). In addition the ships were also fitted with 24-power magnification telescopic gunsights.
Japanese battleship Mikasa