Parallel Resistance Calculator

How parallel resistors combine

Wiring two resistors in parallel gives current more than one path to flow through, which always lowers the total resistance below either individual resistor.

Worked example

For a 100 ohm resistor in parallel with a 200 ohm resistor:

Rtotal = (R1 x R2) / (R1 + R2) = (100 x 200) / (100 + 200) = 66.67 ohms

R1	R2	Combined
100 ohms	100 ohms	50 ohms
100 ohms	200 ohms	66.67 ohms
100 ohms	1000 ohms	90.9 ohms

Notice the combined resistance is always closer to the smaller of the two values - as one resistor becomes much larger than the other, the combined result approaches the smaller resistor's value, since the larger one contributes comparatively little extra current path.