Force rating
Since the question has come up several times, here is a summary of how Force ratings are calculated.
Base Unit Force Evaluation
First the base unit gets a force evaluation. If the unit has a ranged attack, the starting force is the ranged strength ^ 1.45. Otherwise the starting force is strength ^ 1.5. This is multiplied by the unit's movement ^ 0.3. Nukes get +4000.
Then this is multiplied by a bunch of modifiers: * 0.5 if ranged naval * 0.5 if self-destructs when attacking * Half the city attack bonus (So +25% if the unit has +50% when attacking cities) * A Quarter of attack bonuses vs things other than cities * Half the bonus "when attacking" * Half the bonus "when defending" * +25% if paradrop able * -20% if needs to set up to attack * Half the bonus from certain terrain * +20% bonus per extra attack per turn
Individual Unit Force Evaluation
Each individual unit has a Force equal to the Base Unit Force, * multiplied by (number of times promoted +1) ^ 0.3. * multiplied by current health as a percentage.
Civ Force Ranking
The civs Force Ranking is based on the sum of all their units' Force Evaluation (cities are not counted). Only half the Force of naval units is counted. This is multiplied by a gold modifier equal to the square root of current gold, as a percentage. The gold multiplier is constrained to be between 1 and 2, so the max multiplier is 2 which is reached at 10000 gold.
Show Me Some Numbers
Scout 13Archer 19Slinger 19Dromon 23Warrior 27Maori Warrior 27Brute 27Bowman 29Jaguar 36Catapult 39Composite Bowman 39Galleass 41Chariot Archer 42War Elephant 44War Chariot 45Horse Archer 45Trireme 46Spearman 49Ballista 55Persian Immortal 56Horseman 62Hoplite 63Swordsman 64Chu-Ko-Nu 66Quinquereme 69African Forest Elephant 72Battering Ram 80Cataphract 80Crossbowman 81Longbowman 81Companion Cavalry 84Legion 86Mohawk Warrior 86Pikeman 87Landsknecht 87Trebuchet 88Keshik 89Frigate 100Hwach'a 110Longswordsman 118Camel Archer 124Samurai 126Berserker 133Knight 134Conquistador 134Mandekalu Cavalry 134Caravel 134Ship of the Line 139Musketman 144Cannon 151Minuteman 154Janissary 162Gatling Gun 169Musketeer 182Tercio 182Naresuan's Elephant 194Lancer 204Hakkapeliitta 204Sipahi 218Privateer 222Rifleman 243Carolean 243Sea Beggar 244Artillery 245Battleship 269Great War Bomber 290Cavalry 300Hussar 320Triplane 325Turtle Ship 327Cossack 337Norwegian Ski Infantry 345Guided Missile 378Carrier 408Submarine 420Bomber 425Great War Infantry 434Machine Gun 465Fighter 470Foreign Legion 477Ironclad 486Zero 508Anti-Tank Gun 542B17 551Marine 645Landship 703Infantry 720Nuclear Submarine 735Stealth Bomber 771Paratrooper 806Anti-Aircraft Gun 819Destroyer 870Missile Cruiser 888Rocket Artillery 930Tank 948Jet Fighter 988Helicopter Gunship 992Mechanized Infantry 1186Panzer 1223Mobile SAM 1376Modern Armor 1620Giant Death Robot 2977Atomic Bomb 4714Nuclear Missile 7906