Encumbrance
Encumbrance rules determine how much your equipment slows you down. Encumbrance comes in two parts: encumbrance by armor and encumbrance by total weight.
Encumbrance by Armor
Your armor defines your maximum Dexterity bonus to Reflex Defense, your armor check penalty, your speed, and how fast you move when you run (see Armor). Unless your character is weak or carrying a lot of gear, that's all you need to know. The extra gear your character carries, such as weapons and medpacs, won't slow your character down any more than his or her armor already does.
If your character is carrying a really heavy load, however, then you'll need to calculate encumbrance by weight.
Encumbrance by Weight
If you want to determine whether your character's gear is heavy enough to slow him or her down (more than any armor already does), add up the weight of all the armor, weapons, and gear the character is carrying. If the total equals or exceeds the square of one-half your character's Strength score, he or she is carrying a heavy load. For example, a character with Strength 12 is carrying a heavy load if the total weight of his or her armor and gear is 36 kg (0.5 x 12, squared) or more.
When carrying a heavy load, a character takes a -10 penalty on checks made using the following skills: Acrobatics, Climb, Endurance, Initiative, Jump, Stealth, and Swim. A heavy load also reduces the character's speed to three-quarters normal (rounded down). A character can move up to three times his or her speed when running with a heavy load (instead of four times).
Carrying Capacity
The amount of weight that you can lift (in kilograms) is based on your Strength score and determined by the following formula: (Strength score)^2 x 0.5. For example, a character with Strength 15 can lift 112.5 kg (15 x 15 x 0.5).
A character can strain to lift an amount of weight (in kilograms) equal to his Strength score squared, but he or she can only stagger around with it. While overloaded in this way, the character loses any Dexterity bonus to Reflex Defense and can only move 1 square per round (as a full-round action).
A dragged object has less effective weight depending on the resistance of the surface: normal ground, 1/2; smooth surface or wheels, 1/5; completely frictionless (such as pulling an object in zero-g or on a repulsorlift), 1/10. Dragging an object over rough ground is no easier than lifting it.
Bigger and Smaller Creatures
Larger creatures can carry more weight depending on size category: Large (x2). Huge (xS). Gargantuan (xl0). and Colossal (x 20). Smaller creatures can carry less weight depending on size category: Small (x 0.75), Tiny (x 0.5), Diminutive (x 0.25), Fine (x 0.01).