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Power dissipation calculator

Compute the power dissipated by a resistor from current and resistance (P = I²R).

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Need Power dissipated (W)? The Power dissipation calculator derives it from Current (A), Resistance (Ω) in one step. For instance, with Current (A) = 2 and Resistance (Ω) = 100 it returns Power dissipated (W) = 400.

How to use it

  1. Enter your values: Current (A), Resistance (Ω).
  2. Read the result instantly: Power dissipated (W).

Frequently asked questions

How does the Power dissipation calculator work?

It takes Current (A) and Resistance (Ω) and derives Power dissipated (W) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Current (A) and Resistance (Ω). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Current (A) = 2 and Resistance (Ω) = 100, the calculator returns Power dissipated (W) = 400. 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 Current (A) = 4 and Resistance (Ω) = 200 instead, Power dissipated (W) goes from 400 to 3,200 — 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 Current (A) = 1 and Resistance (Ω) = 50, Power dissipated (W) comes out at 50. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

What is the difference between the Power dissipation calculator and the Power Factor Calculator?

This one returns Power dissipated (W); the Power Factor Calculator returns Result. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Amperage Calculator is the closest one after this: Convert a load in watts and a supply voltage into the current drawn in amps.

What else is worth having open alongside it?

RC time constant calculator and Wire resistance calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.ExplainerHow Many Cables Fit in a Conduit? It Is a Code Question, Not a Geometry QuestionThe 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.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.How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.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.