A full walkthru of a drivetrain analysis using this Torque/Amp Calculator is available:  
Input Values 

Torque Constant (Kt)  Torque produced by this motor for each amp consumed. 
Voltage Constant (Kv)  RPM produced by this motor for each volt applied. 
Operating Voltage  Maximum recommended voltage for this motor. Enter the voltage available to your robot, if it is different than the value given. 
Actual Robot Weight  True weight of the Robot. For calculations it is assumed that 100% of this weight is supported by driven wheels. For robots that have idler wheels, ball casters, skids, or similar supporting some of the weight you can adjust the value in the 'Tire Coefficient of Friction' field below  see example there. 
Motorsperside  The robot is assumed to be symmetrical, with an equal number of drive motors on each side. For robot with 2 motors (1 per side) enter '1' here. Four motors (2 per side) enter '2' here, and so on. 
Wheel Diameter  Diameter of your drive wheels, in inches. 
Tire Coeff of Friction  The friction coefficient of the tire, i.e. how 'grippy' it is. The default value '0.9' represents a typical best case. You may enter lower values for known 'slick' conditions, or to compensate for a portion of the robot weight being supported by other than driven wheels. Example: for a robot with 60% of the weight on the driven wheels under good traction conditions, enter the product of 60% and 0.9, which is '0.54'. 
Gear Ratio  Gearing after the motor output shaft. For gearmotors with no additional reduction or increase enter '1'. See Optimum Gearing Tips for ratio selection help. 
Average % of Peak Drain  Estimate the average current drain as a percentage of the calculated peak load. Example: if you expect to spend 50% of combat time at full power and 50% at 25% of full power, enter (100+25)/2 = '62.5'. The default of 70% is based on actual combat power usage. 
Calculated Values 

Torque Per Motor  Torque required at the output shaft of a given motor to spin the wheel(s) driven by that motor (the "breakaway torque"). 
Amps Per Motor  Amperage required to deliver the breakaway torque by a single motor 
Theoretical Top Speed  Top speed this drive train would reach at the operating voltage, given sufficient time and distance and assuming the motor can produce the required power. 
Total Peak Amps  Total Amperage for all motors at breakaway torque. 
AH Required  3 Min  Battery capacity required to finish a 3 minute match at the % average drain specified. 
AH Required  5 Min  Battery capacity required to finish a 5 minute match at the % average drain specified. 
About the Calculator 

History  The original Team Tentacle Torque/Amp Calculator was written by Steve Judd of Tentacle Combat Robotics. A highly respected combat robot builder and a selfless supporter of the sport, Steve died in 2010 after a long fight with repiratory disease. His loss was deeply felt in the community. 
This Version  Following Steve Judd's death, Team Run Amok began a series of updates to the calculator that include support for new motors, expanded help files, and revised formating. Steve's core program is unchanged, and a link back to the original version appears in the upper right corner of the 'Reloaded' calculator. 
Other Versions  Richard Stuplich from Team Killerbotics has also produced an updated version of the torque/amp calculator. You can find Richard's version here: Killerbotics Torque/AmpHour Calculator 