Parallel resistor calculator
Any number of resistors in parallel (and series) — plus reverse mode: what to parallel with what's in your drawer.
How it works
Resistors in parallel share the same voltage, and their currents add — so conductances (1/R) add: 1/R = 1/R1 + 1/R2 + …. In series the same current flows through each, so resistances simply add.
The reverse mode answers the bench question this calculator really exists for: "I need 2.5k and I don't have one — what do I put in parallel with my 10k?"
Common questions
Each added resistor is another path for current — more paths, more total current at the same voltage, which is the definition of less resistance. The combined value is always smaller than the smallest resistor in the set.
Product over sum: R = (R1·R2)/(R1+R2). Two equal resistors halve; a resistor paralleled with one 10× bigger barely moves (10k ∥ 100k ≈ 9.1k) — handy for fine-tuning a value you already placed.
Each parallel resistor sees the full voltage, so it dissipates V²/R independently — smaller resistors in the set run hotter. Two equal resistors in parallel each take half the current, which is a legitimate way to split power across two cheap parts.