Mjölner was based on the design the Spica class designed in Italy.
Small and designed for coastal operation, the vessel was named after Thor's hammer, Mjölner.

Displacement was 750 tonnes (740 long tons; 830 short tons) standard and 960 tonnes (940 long tons; 1,060 short tons) full load.
Overall length was 256 feet (78.03 m), beam 26 ft 3 in (8.00 m) and draught 8 ft 10 in (2.69 m).
A crew of 100 officers and ratings was carried.

Machinery consisted of two Penhoët A oil-fired boilers, which supplied steam to two de Laval geared steam turbines, each driving its own propeller.
The turbines were rated at 16,000 shp (12,000 kW) to give a design speed of 30 knots (35 mph; 56 km/h).
190 long tons (190 t) of fuel was carried to give a range of 1,260 nautical miles (2,330 km) at 20 knots (23 mph; 37 km/h).

The main armament consisted of three 10.5 cm (4 in) K/50 M42 guns produced by Bofors.
These were placed in separate mounts, one on the fore deck, one on the aft deck and one on the aft superstructure.
Air defence consisted two 40 mm (1.57 in) K/60 M36 and two 20 mm (0.79 in) K/66 M40 individually mounted anti-aircraft autocannons, also provided by Bofors.
Three torpedo tubes for 53 cm (21 in) torpedoes were triple mounted aft of the superstructure and two depth charge throwers were mounted further towards the stern.
42 mines could also be carried for minelaying.
Mjölner was based on the design the Spica class designed in Italy. Small and designed for coastal operation, the vessel was named after Thor's hammer, Mjölner.
Displacement was 750 tonnes (740 long tons; 830 short tons) standard and 960 tonnes (940 long tons; 1,060 short tons) full load. Overall length was 256 feet (78.03 m), beam 26 ft 3 in (8.00 m) and draught 8 ft 10 in (2.69 m). A crew of 100 officers and ratings was carried.
Machinery consisted of two Penhoët A oil-fired boilers, which supplied steam to two de Laval geared steam turbines, each driving its own propeller. The turbines were rated at 16,000 shp (12,000 kW) to give a design speed of 30 knots (35 mph; 56 km/h). 190 long tons (190 t) of fuel was carried to give a range of 1,260 nautical miles (2,330 km) at 20 knots (23 mph; 37 km/h).
The main armament consisted of three 10.5 cm (4 in) K/50 M42 guns produced by Bofors. These were placed in separate mounts, one on the fore deck, one on the aft deck and one on the aft superstructure. Air defence consisted two 40 mm (1.57 in) K/60 M36 and two 20 mm (0.79 in) K/66 M40 individually mounted anti-aircraft autocannons, also provided by Bofors. Three torpedo tubes for 53 cm (21 in) torpedoes were triple mounted aft of the superstructure and two depth charge throwers were mounted further towards the stern. 42 mines could also be carried for minelaying.
HSwMS Mjölner (32)