How this calculator works
Resistors turn electrical energy into heat. Series resistors share a current and divide the source voltage; parallel resistors share voltage and divide current. The equivalent resistance determines total current, then each resistor power follows from its own voltage and current. These are ideal fixed resistances without temperature rise feedback. Component ratings and cooling still need to be checked separately.
Formula
Series Req = sum(Ri); parallel 1/Req = sum(1/Ri). Ptotal = V²/Req. For each resistor Pi = Vi Ii = Ii² Ri.
Worked example
Resistors 2 and 3 ohm in series across 10 V have Req = 5 ohm, current 2 A and total power 20 W. Two 2 ohm resistors in parallel across 10 V have Req = 1 ohm and dissipate 100 W in total.
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Frequently asked questions
Can I include a zero-ohm resistor?
This finite passive-network model requires positive resistances. A short circuit needs separate handling.
How do I choose a resistor power rating?
Compare the individual wattage with a manufacturer rating and its temperature derating curve; total power alone is insufficient.
Can the tool solve a mixed series-parallel circuit?
Reduce each simple group first, then use its equivalent resistance as one entry in the next group.