Total Resistance Calculator
Total resistance is the single resistor that behaves exactly like a whole network. Series connections add, parallel connections combine reciprocally, and mixing the two is where most mistakes happen.
Total resistance
600
- If wired in series
- 600
- If wired in parallel
- 54.5455
- Current drawn
- 0.02
- Power dissipated
- 0.24
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
Series: R = R1 + R2 + R3. Parallel: 1/R = 1/R1 + 1/R2 + 1/R3
- R
- The total or equivalent resistance, in ohms
- R1, R2, R3
- The individual resistances, in ohms
- I
- Current, in amperes, found from Ohm's law
How to check the result by hand
- 1
Identify how the resistors are connected
Trace the current path. If it passes through every resistor one after another they are in series; if each one connects the same two nodes they are in parallel.
- 2
Add for series
100 plus 200 plus 300 is 600 ohms. The total is always larger than the largest individual resistor, which is the quick check.
- 3
Add reciprocals for parallel
1/100 plus 1/200 plus 1/300 is 0.01 plus 0.005 plus 0.003333, which is 0.018333. Taking the reciprocal gives 54.5455 ohms.
- 4
Apply Ohm's law to the equivalent
With 12 volts across 600 ohms the current is 12 divided by 600, which is 0.02 amperes. The same current would flow through a single 600 ohm resistor.
For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Total Resistance page.