Electrical Power Calculator
Power and resistance from voltage and current (P = V × I).
Result
Power (W)
1,150.00
Resistance (Ω)
46.00
How it works
Electrical power is the rate at which energy is used: P = U × I, volts times amps, in watts. A device drawing 2 A at 230 V consumes 460 W. Dividing voltage by current gives the resistance, R = U ÷ I, by Ohm's law. Watts are what your electricity bill counts (as kilowatt-hours), and what determines the heat a component must shed. It is also what sizes your wiring: the same 2,300 W drawn at 230 V needs 10 A, but at 115 V it needs 20 A — twice the current, so thicker cable and a bigger breaker. Two useful rearrangements when you know only two of the three quantities: P = I²·R (handy for heating elements and cable losses) and P = U²/R. And a practical note: for household appliances the wattage is printed on the rating label, so you rarely need to measure the current yourself.
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Frequently asked questions
How do I get watts?
Multiply the voltage by the current: a 230 V appliance at 5 A draws 1150 watts.
How is resistance found?
By Ohm’s law, R = V ÷ I — voltage divided by current.
Why do the same watts need more amps at a lower voltage?
Because power is voltage times current. To keep P constant while U falls, I must rise: 2,300 W is 10 A at 230 V but 20 A at 115 V — hence thicker cables in 110 V countries.
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