[SpEEdyBL]

First there are many things to consider and i wont explain all of them in this post. Ideally, if a motor were to be 100% efficient, it would put out the same amount of power (force x velocity) as power from the battery (volts x amps). As you know, more volts = proportionally more rpm and more amps = proportionally more torque. Torque is measured from a certain distance away from the pivot point so lets take our measurements 1 meter away from the center of the shaft to make it simple. Now kv values are given for all motors and torque values are not explicitly given, but you will see why it doesn't matter in a minute. First, kv must me converted in to velocity. 1 rpm = 2pi/60 radians per second = 2pi/60 meters per second 1 meter away from the center of the shaft. All you have to do now is find what torque value multiplied by that velocity will equal the volts x amps. For instance, if you had a 1000 kv motor and applied 10 volts and it drew 10 amps, power would be 100 watts, velociti (radians per second) would be 2 x 10000pi/60 ~1047 meters per second. Solve the equation 100 = 1047x and x ~ .0955 newtons of force 1 meter away from the shaft. If you do this equation again for a 2000 kv motor on the same volts and amps, you get half the torque. So, torque in newton meters per amp (nm/amp) ~ 9.55/motor kv. Once converted to oz*in/amp, kt ~ 1350/kv. This works for all brushless motors. To put this in perspective, the 8xl which has roughly 2100 kv will have more than twice the kt as the HV4.5 which has 4800 kv. That means if both motors pulled the same number of amps, the 8xl would have more than twice the torque and ideally (assuming equal voltage also) both motors would have the same power output.