Find the total resistance of resistors wired in parallel — add as many as you need.
How to Use the Parallel Resistor Calculator
Enter a value for each resistor in the list — two rows to start, with buttons to add more or remove down to a single one. The total recalculates the instant any value changes.
Resistors in parallel always add up to less than the smallest one in the group, which trips people up the first time they see it — more resistors, less total resistance, the opposite of what "adding more" suggests everywhere else in life:
1 ÷ Rtotal = 1 ÷ R1 + 1 ÷ R2 + ... + 1 ÷ RnTwo identical 100Ω resistors in parallel land on exactly 50Ω — half of one, because each branch is doing half the work of carrying current. Add a third identical resistor and it drops to 33.3Ω, since three equal paths now share the load evenly. The more paths current has to flow through, the less total resistance the circuit as a whole presents, even though nothing about any individual resistor changed.
A resistor value of zero or less isn't physically meaningful here, so the calculator flags it rather than dividing by zero or returning a negative total that wouldn't correspond to anything real.