Resistors in Series

Resistors in Series are pretty straight forward. The total resistance, for two or more resistor, is equal to the sum of the resistances.

In the area on the right, enter your resistors values in the spaces provided and then click outside the box to find R Total for the resistors in Series. The drawing will reflect the entered resistor values.

Note: If you only wish to calculate the resultant value of two resistors in series, set one of the boxes to Ø (zero). Do not just leave it blank as that would generate an open circuit.

Resistors in Parallel

The drawing on the right shows two equations that cover resistors in parallel. The first one can be used if you are only dealing with 2 resistors in Parallel. The second equation is used when there are more than 2 resistors in Parallel.

Enter your resistors values in the spaces provided and then click outside the box to find R Total for the resistors in Parallel.

Note: If you only wish to calculate the resultant value of two resistors in parallel, leave one of the boxes empty. Do not enter Ø (zero), or a space, as that would short out all the other resistors.

• The resultant value, of two or more resistors in parallel, is always less than the lowest resistor.

• If the resistors are of equal value, the resultant value is equal to the value of one of the resistors, divided by the number of resistors. For example, if there are three 100 Ohm resistors in parallel the resultant value will be 100/3 = 33.333 Ohms.

• If a very large resistor and a very small resistor are in parallel, the resultant value will only be a little bit less then the smaller resistor. For example, if there are a 10K Ohm resistor in parallel with a 100 Ohm resistor the resultant value will be 99 Ohms. Just 1 Ohm less than the lower value resistor.