Calculate Voltage, Amperes, Resistance and Watts using Ohms Law and Power formula.

Instructions: Input any two known values for voltage, amperes, resistance or watts, and click the calculate button. The calculator will calculate the other unknown values and display the answer below. The value for voltage must be in volts, amperes must be in amps, resistance must be in ohms, and power must be in watts. You must input two known values, and you cannot input only one, three or four values or an error will occur.



(Answer will appear here and in the input boxes.)

According to Merriam Webster dictionary, ohms law is " a law in electricity: the strength of a direct current is directly proportional to the potential difference and inversely proportional to the resistance of the circuit." Potential difference in this definition is another way of saying voltage. Another way of stating this definition using math is with the following equations:

Voltage = Current * Resistance

Current = Voltage / Resistance

Resistance = Voltage / Current

In the above equations the symbol * means to multiply and the symbol / is for divide. Why are these equations important? They are important because the small engine mechanic, motorcycle mechanic or technician can use these equations to analyze electrical circuits. For example, if the technicians measures the current through a load and the voltage across the load, than ohms law can be used to calculate the amount of resistance created by the load. These specifications can be checked in the manual for the equipment being worked on to help determine if a component is bad or good.

Power is the amount of energy used per unit time, and when dealing with electricity, power is defined using the following formula's:

Power = Voltage * Current .....or

Power = Current^2 * Resistance ....or

Power = Voltage^2 / Resistance

In the above power formula's ^2 means to square the value. The symbol / means to divide, and * means to multiply.