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Ohm's Law Calculator

Solve Ohm's law the complete way. Enter any two of voltage, current, resistance, and power, and WattSimple fills in the other two from the full power wheel, then shows the wire ampacity for the resulting current.

Enter any two values. WattSimple solves the other two.

Power

600 W

Voltage
120 V
Current
5 A
Resistance
24 Ω
Power
600 W

NEC wire & breaker for this load

Breaker
15 A
Min. copper wire (75°C)
14 AWG

Copper, 75°C terminations, NEC Table 310.16. Real installs may need derating for ambient heat, conduit fill, or voltage drop. Full wire & breaker chart. Always confirm with a licensed electrician + local AHJ.

Measure the real amps and volts

The converter works from nameplate or assumed figures. A clamp meter reads the actual current on one conductor without breaking the circuit; clamped around a whole cord it reads close to zero. A multimeter reads the voltage at the receptacle or terminals. Opening a panel or a live box is work for someone qualified.

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Frequently asked questions

Ohm's law states that voltage equals current times resistance: V = I × R. Combined with the power equation P = V × I, it forms the 'power wheel' linking voltage (V), current (A), resistance (Ω), and power (W), any two of which determine the other two.

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APA

WattSimple. (2026, July 19). Ohm's Law Calculator. https://wattsimple.com/convert/ohms-law

MLA

"Ohm's Law Calculator." WattSimple, 19 July 2026, https://wattsimple.com/convert/ohms-law.

Chicago

WattSimple. "Ohm's Law Calculator." Last modified July 19, 2026. https://wattsimple.com/convert/ohms-law.

HTML link

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Sources & standards

This tool's methodology and data follow US standards and authoritative public datasets: