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Parallel resistor calculator

Compute the total resistance of resistors connected in parallel.

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Enter Resistances (Ω, comma-separated) and the Parallel resistor calculator works out Total resistance (Ω) straight away. For instance, with Resistances (Ω, comma-separated) = 100, 220, 330 it returns Total resistance (Ω) = 56.897.

How to use it

  1. Enter your values: Resistances (Ω, comma-separated).
  2. Read the result instantly: Total resistance (Ω).

Frequently asked questions

How does the Parallel resistor calculator work?

It takes Resistances (Ω, comma-separated) and derives Total resistance (Ω) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

A single value: Resistances (Ω, comma-separated). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Resistances (Ω, comma-separated) = 100, 220, 330, the calculator returns Total resistance (Ω) = 56.897. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Resistances (Ω, comma-separated) = 100, 231, 363 instead, Total resistance (Ω) goes from 56.897 to 58.535 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Resistances (Ω, comma-separated) = 100, 220, Total resistance (Ω) comes out at 68.75. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

At the bench: sizing a resistor for an LED, reading a colour band, working out a divider ratio, and checking a part will not cook.

What is the most common mistake?

Choosing a resistance and forgetting the power rating. A value that is electrically right will still burn if the package cannot dissipate what passes through it — check the watts as well as the ohms.

Is there a tool for the next step?

LED resistor calculator is the closest one after this: Find the series resistor needed to drive an LED from a supply voltage.

What else is worth having open alongside it?

Resistor Color Code Calculator and Series capacitor calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Ohm's law and the divider formulas are exact. Colour bands follow the IEC standard; real components carry a tolerance, so a nominal value and a measured one will not match exactly.

Further reading

All guides →
ExplainerResistors in Series and in Parallel: The Formulas, and the Three Things They Do Not Tell YouSeries adds, parallel adds reciprocals — that part is easy. The parts that catch people: which member dominates the answer, why two 5 % resistors in parallel are still 5 %, and why the smallest resistor in a parallel pair takes the largest share of the power.ExplainerThe Voltage Divider: The Formula Is Trivial, the Assumption Behind It Is NotVout = Vin·R2/(R1+R2) is only true when nothing is connected to the output. Draw current and the voltage collapses, by an amount that follows one exact law. Here is that law, the ten-times rule checked against it, and why a lower-resistance divider costs you power forever.How-toHow to Calculate an LED Series ResistorSize the series resistor for any LED with one formula: R = (Vs − Vf) / I. Follow the steps, see a worked 5 V example, and pick the right resistor.ExplainerWhat Is Ohm's Law? V = I × R Explained SimplyOhm's law links voltage, current, and resistance with one equation: V = I × R. Learn the triangle trick and see worked examples.ExplainerWhat Is Voltage Drop? Why Long Wires Lose VoltageVoltage drop is the voltage lost along a wire due to its resistance. Learn how length, gauge, and current affect it, and why it matters for your circuits.ExplainerScreen Resolution, Pixel Density, and the Numbers Marketing UsesA diagonal plus an aspect ratio gives you width and height by Pythagoras, and the answer is not what the marketing implies: a 27-inch 21:9 has 16.2% less area than a 27-inch 16:9. Then pixels per degree, which shows the highest-PPI phone is not the sharpest thing you own.