The diagram to the right is simplest form of a circuit. It consists of a Voltage Source, E, connected to a Resistance, R, and indicates the Current, I, that flows through the circuit. Not shown, but still a prime factor, is the Power, P, dissipated by the resistor.

All of these circuit parameters are related. This relationship is known as Ohms Law.

As you can see from the equations on the left, only two parameters are necessary to calculate any of the other parameters. For example, if you only have Voltage and Current (E and I), Resistance (R) can be calculated with the relationship R=E/I and Power (P) can be calculated with P=E*I.

The form on the right can be use to calculate any of the equations listed above. Just select the type of input data and enter the values. The output text area will list the input values followed by the missing elements.

Notice, in the equation table above, that as you change the input data type selectors, the equations that will be used for calculating the missing data will be highlighted.

If you select the same input data type in both selectors, no meaningful calculations can be performed.

Voltage Current Resistance Power	Voltage Current Resistance Power
x

The equations assume that Voltage is in Volts, Current is in Amperes, Resistance is in Ohms, and Power is in Watts. If any of the quantities are expressed in other units they must be converted to the base units. For example, milliAmpers must be converted to the equivalent fraction of an Ampere.