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Watts, Amps & Volts Calculator

Convert between electrical power (watts), current (amps), and voltage (volts) using Ohm's Law — P = I × V.

Select which value you want to calculate
Electrical power in watts
Electrical current in amperes
Voltage in volts (US: 120 V or 240 V)

Results

Calculated Value1,200.000
Power1,200.00 W
Current10.000 A
Voltage120.00 V

📖What is it?

The Watts, Amps & Volts Calculator applies Ohm's Law for electrical power (P = I × V) to convert between electrical power in watts, current in amperes, and voltage in volts. This is essential for sizing circuits, choosing breakers, and understanding appliance power draw.

🎯How to use

1. Select what you want to solve for (Watts, Amps, or Volts). 2. Enter the other two known values. 3. The "Calculated Value" shows the result; the three reference outputs show your complete electrical picture.

💡Example scenario

A 1,500 W space heater on a 120 V circuit: solving for Amps → 1500 ÷ 120 = 12.5 A. A 15 A circuit breaker (rated to 80% = 12 A continuous) would be overloaded — a 20 A circuit is required.

🏆Pro tip

NEC code requires circuits be loaded to no more than 80% of their rated capacity for continuous loads (3+ hours). A 15 A breaker should carry no more than 12 A continuously; a 20 A breaker, no more than 16 A. Always consult a licensed electrician for panel work and new circuit installation.