wikiHow Total Resistance in Circuits Calculator To calculate the total resistance in a circuit, you need to know the resistance values of each individual resistor in the circuit and how they are connected. There are two basic ways that resistors can be connected: in series or in parallel. When resistors are connected in series, the total resistance is simply the sum of the individual resistances: Total Resistance = R1 + R2 + R3 + ... For example, if three resistors are connected in series with values of 10 ohms, 20 ohms, and 30 ohms, the total resistance would be: Total Resistance = 10 ohms + 20 ohms + 30 ohms = 60 ohms When resistors are connected in parallel, the total resistance is calculated using the following formula: Total Resistance = 1 / (1/R1 + 1/R2 + 1/R3 + ...) For example, if two resistors are connected in parallel with values of 10 ohms and 20 ohms, the total resistance would be: Total Resistance = 1 / (1/10 ohms + 1/20 ohms) = 6.7 ohms It's important to note that in more complex circuits, resistors may be connected in both series and parallel. In these cases, you would need to calculate the total resistance of each series and parallel branch and then combine them using the same formulas. Page