Resistor Series & Parallel Calculator
Parallel is always below the smallest. That is the check.
Work out Resistor Series & Parallel. Parallel is always below the smallest. That is the check. States the assumption instead of hiding it.
Comma or space separated. Any number of resistors.
Total resistance
59.977 Ω
3 resistors · Parallel — conductances add
In series, resistances simply add, and the total always exceeds the largest single resistor. In parallel the reciprocals add, and the total is always below the smallest — that is the sanity check worth memorising, because a parallel answer larger than any element means the arithmetic went in backwards. Two equal resistors in parallel give exactly half; three give a third. The shortcut only works for equal values, which is why the general reciprocal form is used here. Power matters as much as resistance in practice. In series every resistor carries the same current, so the largest value dissipates the most heat; in parallel every one sees the same voltage, so the smallest does.
How the Resistor Series & Parallel Calculator works
Total resistance for any number of resistors in series or parallel, with the sanity check that catches the commonest mistake — a parallel total larger than any single resistor means the arithmetic went in backwards.
Also known as: two resistors in parallel · equivalent resistance calculator · combine resistor values · resistors in series formula
Frequently asked questions
How do I calculate resistors in parallel?
Add the reciprocals and take the reciprocal of the total. For two resistors the shortcut is the product over the sum. The answer is always smaller than the smallest resistor in the set.
How do resistors add in series?
They simply add. Current has only one path, so every resistor drops part of the voltage, and the total always exceeds the largest single value.
Why is parallel resistance always smaller?
Because you are adding paths for current, not obstacles. Every extra route makes it easier for current to get through, so the effective resistance falls no matter what you add.
Do two equal resistors in parallel always halve?
Yes, and three equal ones give a third. The shortcut only works for equal values, which is why the general reciprocal formula is used here.
Which resistor gets hottest?
In series, the largest value — every resistor carries the same current, and power is I²R. In parallel, the smallest, since they all see the same voltage and power is V²/R.
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