Convert
Converting Watts to Amps:
Amps = Watts/Volts     Example: 12 watts/12 volts = 1 amp

Converting Amps to Watts:
Watts = Amps x Volts    Example: 1 amp * 110 volts = 110 watts

Converting Watts to Volts:
Volts = Watts/Amps    Example: 100 watts/10 amps = 10 volts

Converting Volts to Watts:
Watts = Amps x Volts    Example: 1.5 amps * 12 volts = 18 watts

Converting Volts to Amps at fixed wattage:
Amps = Watts/Volts    Example: 120 watts/110 volts = 1.09 amps

Converting Amps to Volts at fixed wattage:
Volts = Watts/Amps    Example: 48 watts / 12 Amps = 4 Volts

Explanation:
Amps are how many electrons flow past a certain point per second.  
Volts is a measure of how much force that each electron is under.  Think of water in a hose.  
A gallon a minute (think amps) just dribbles out if it is under low pressure (think voltage).  
But if you restrict the end of the hose, letting the pressure build up, the water can have 
more power (like watts), even though it is still only one gallon a minute.  
In fact the power can grow enormous as the pressure builds, to the point that a water knife 
can cut a sheet of glass.  In the same manner as the voltage is increased a small amount of 
current can turn into a lot of watts.

Common Conversions:
km = miles / .6214                miles = km / 1.6093
mm = inch / .03937                inch = mm / .254  aka 2.54 cm
metre = yard / 1.0936             yard = metre / .9144
sq cm = sq in / .1550             sq in = sq cm / 6.4516
sq m = sq yard / .1550            sq yard = sq m / .8361
sq km = sq mile / .3861           sq mile = sq km / 2.59 = 640acres
hectare aka ha = acre / 2.4711    acre = ha / .40468 aka 4840 sq yards

USgallon/4 quarts = UKgallon / 3.7854L     UKgallon = USgallon / 4.5461L aka 8 metric pints 
pint/16 fl. oz. = UKpint / .4371L          UKpint = USpint / .5683L aka 20 metric oz.
USounce = ml / 29.574                      UK fl. oz. = ml / 28.413

USpound/16oz = kg / .4536          kg = USpound / 2.2046

1 joule (J) is equal to one newton metre (N.m)
electronvolt (eV) to J: 1.6021892E-19 (1e*1V)
erg to J: 1E-7
foot pound-force (ft.lbf) to J: 1.35582
calorie (cal) to J: 4.1868
kilogram-force metre (kgf.m) to J: 9.80665
British Thermal Unit (Btu) to J: 1.05506E3
watt hour (W.h) to J: 3.6E3
kilowatt hour (kW.h) to J: 3.6E6
therm to J: 1.05506E8 (1E5 Btu)
1 watt (W) is equal to one joule per second (J/s or m2kgs-3)
foot pound-force per second (ft.lbf/s) to W: 1.35582
kilogram-force metre per second (kgf.m/s) to W: 9.80665
horsepower (metric) to W: 7.35499E2 (75 kgf.m/s) 
horsepower (hp) to W: 7.45700E2 (550 ft.lbf/s)

Electric Vehicle Calculator Equations:
numBatteries = (voltage / batteryVoltage) * numString;
totalBatteryWeight = numBatteries * batteryWeight;
totalChargerWeight = chargerWeight;
totalControllerWeight = controllerWeight;
totalMotorWeight = motorWeight;

weightAdded = totalBatteryWeight +
   totalChargerWeight +

   totalControllerWeight +

   totalMotorWeight +

   miscWeight;
totalWeight = weightAdded + curb_weight - weightRemoved;

torqueMult = 840.34 / revPerMile;
rollingForce = (totalWeight * (rr + bs)) * cos (atan (incline/100));
inclineForce = totalWeight * sin (atan (incline/100));
drag = (dragCoefficient * frontArea * pow (speed, 2))/391;
windFactor = (((.98 * pow(wind/speed, 2)) +
   (.63 * (wind/speed))) * windFactor) -
   (.4 * (wind/speed));

windDrag = drag * windFactor;
dragForce = rollingForce + drag + windDrag + inclineForce;
totalDrag = dragForce * torqueMult;
hp = (totalDrag * speed * revPerMile)/ (315120 * drive_efficiency);
torque = totalDrag / (gearRatio * drive_efficiency);
motor_rpm = (speed * gearRatio * revPerMile) / 60;
motorVolts = (rpm * motorD) / ((motorA/(pow (torque, motorB))) + (motorC));
motorAmps = pow ((torque / motorK), (1/motorN));
batteryVolts = voltage;
batteryPower = motorVolts * motorAmps * (controllerEfficiency /100);
batteryAmps = (power / voltage) / numString;
range = (puekertNum/ pow (batteryAmps, puekertExp)) * speed;