So kg.cm is kg force x centimetre distance. ... Other torque units include foot-pound, Newton-metre, dyne-centimeter (!) ... In your case 3 kg.cm means that a "force" of 3 kg acting at a radius of 1 cm would produce the same amount of torque as your motor. Equally that could be 0.1 kg x 30 cm, or 10 kg x 0.3 cm or ...
