![]() | Series Values add together! The equivalent value of the resistors is Req = R1 + R2 + R3 ... |
Resistors in series increase value: The equivalent value is always greater than the biggest!

Parallel
(1 ÷ Req) = (1 ÷ R1) + (1 ÷ R2) + (1 ÷ R3) ...
If two in parallel formula can be simplified to
Req = (R1 × R2) ÷ (R1 + R2)
Resistors in parallel reduce value: The equivalent value is always less than the smallest!
For combinations reduce parallel into equivalent value first, then calculate series value to give current/voltage