The Planets.nu Military Score is based on the VGA Planets AutoScore game add on and uses the following rules:
Military Score takes each item to be added to the race's total score and breaks it down by each item's cost of construction, both minerals and money. The value is 1 point for each MegaCredit and 5 points for each KT of mineral used in construction. These points are added together for each item of military strength in the race's empire to give that race's total Military Score.
Fixed-position items only receive half-credit as they are considered to be less of a threat to a mobile fleet.
The following are the only items that count towards each race's Military Score:
WARSHIPS: Any ship with a Beam, Torpedo Tube or Fighter Bay is considered a warship for Military Score purposes (yes, even a Q-Tanker). Each warship's value is totaled based on the entire cost of the ship. This includes the cost of the Hull, Engines, Beams, Torpedo Tubes, Torpedoes and Fighters (always scored at 125 each, regardless of the actual cost).
Totals do not include cargo on board.
The additional MegaCredits required to clone a starship do not count towards the Military Score of the starship, only the normal build costs.
STARBASE DEFENSES: The cost of a starbase's Defense Posts and Fighters are totaled for addition to the race's Military Score. Torpedoes in storage and uncompleted ships do not count. Each fighter contributes 62.5 points and each defense post contributes 7.5 points towards the military score, after being halved. The starbase itself, and the level of tech on the starbase, do not contribute to the military score.
PLANETARY DEFENSES: The cost of the planet's Defense Posts are totaled for addition to the race's Military Score. One supply plus ten MegaCredits, halved, equals 5.5 score points per defense point, after being halved. The beams and fighters that a planet defends itself with are not counted towards the military score, as they're a direct by-product of the number of defense posts on the planet.
MINEFIELDS: The total number of mine units contained in all minefields, owned by that race, are totaled, then divided by 100 (this assumes Mark 8's) and fractions are truncated. The cost of this many Mark 8 torpedoes is then totaled for addition to the race's Military Score (in terms of per mine unit, this would yield a value of .69/2 = .345 points per mine unit). The score is halved because a torpedo that was a mobile military device is now a static military device, and usually has less tactical value.
NOTE: This last number has been reported to be off by a minor amount; apparently, the mineral cost of the Mk8 torpedoes is not being included in Military Score reporting.