Parallel Resistor Calculator
Need a value that is not in your kit, or combining loads on one rail? Enter up to four resistors in parallel and get the equivalent resistance instantly, along with the total conductance.
Leave a field at 0 to skip it. Enter in ohms — 4.7 kΩ is 4700.
Formula & how it works
Equivalent resistance is the reciprocal of summed reciprocals: R = 1 ÷ (1/R1 + 1/R2 + …). Conductance is that sum, G = 1/R1 + 1/R2 + …, in siemens. For two resistors the shortcut is R1 × R2 ÷ (R1 + R2).
Worked example
Two 100 Ω resistors in parallel give 1 ÷ (0.01 + 0.01) = 50 Ω. Add a 200 Ω in parallel and it drops to about 40 Ω. Notice the result is always below the smallest resistor in the group.
Combining resistors
Reaching odd values
Standard resistor kits skip a lot of values, but parallel combinations fill the gaps. Two equal resistors halve the value; unequal pairs land in between. It is a common trick for hitting a specific target when you don't have that exact part on hand.
Sharing the load
Parallel resistors also split current between them, so the same total power is spread across more parts. That lets several ordinary resistors together handle more wattage than one could alone, which is useful for things like dummy loads and bleed resistors.
The result trends down
Because each added path gives current another route, the combined resistance is always lower than the smallest branch. If you need a value higher than any single resistor, that is a job for series wiring rather than parallel.