Power from Current and Voltage

The Electrical Power calculator computes the power based on Ohm's Law using electrical potential or voltage (V) and current (I).

INSTRUCTIONS: Choose units and enter the following:

• (V) Potential (voltage)
• (I) Current.

Electrical Power: The calculator returns the electrical power in watts.  However, this can be automatically converted to other power units via the pull-down menu.

General Information

 For more information on the relationship between electrical power, current, resistance and potential, see the Ohm's Law Calculator.

Ohm's Law Calculator 

• Power: (watts, milliwatts, kilowatts, horsepower)
  • P = I • V:  This computes the power (watts) as a function of current (amps) and potential (volts).
  • P = R • I²: This computes the power (watts) as a function of current (amps) and resistance (ohms).
  • P = V² / R: This computes the power (watts) as a function of potential (volts) and resistance (ohms).
• Potential: (volts, millivolts)
  • V = I • R :  This computes the potential (volts) as a function of current (amps) and resistance (ohms).
  • V = P / I: This computes the potential (volts) as a function of power (watts) and current (amps).
  • V = √(P • R) : This computes the potential (volts) as a function of power (watts) and resistance (ohms). 
• Resistance: (ohms, milliohms, kiloohms)
  • R = V²/P: This computes the resistance (ohms) as a function of potential (volts) and power (watts).
  • R = P / I² : This computes the resistance (ohms) as a function of power (watts) and current (amps).
  • R =  V / I : This computes the resistance (ohms) as a function of potential (volts) and current (amps).
• Current: (amps, milliamps, microamps, gilberts)
  • I = V / R: This computes the current (amps) as a function of potential (volts) and resistance (ohms).
  • I = P / V : This computes the current (amps) as a function of the power (watts) and the potential (volts).
  • I = √(P/R): This computes the current (amps) as a function of the power (watts) and the resistance (ohms).

Power is the amount of energy consumed or produced over time.

• Power is a measurement of the energy used to move vehicles (automobiles, trucks, tractors, trains, boats and airplanes).
• Power is the measurement of energy consumed by a motor and transferred to the drive or wheels. 
• Power is the amount of electrical energy consumed or produced by a system over time such as the energy produced by a hydroelectric dam or energy consumed by an electrical motor.

Power Units

Power is most commonly measured in watts (W).  One watt is equal to one joule per second (1 W = 1 J / 1 s).  Power is also measured in horsepower (hp) where 1 horsepower equals 745.7 watts.  Power is also measured in heat energy transfer as BTUs per hour (BTU/h).

Power Calculators

• Power from Change in Energy over Time
• Power based on Force and Velocity
• P = ΔE / Δt
• ΔE = P * Δt
•  Δt = ΔE / P 
• Power Dissipated by Friction
• Power from Force, Distance and Time
• Power from Resistance and Current
• Power from Voltage and Resistance
• Power from Current and Voltage
• Power textbook chapter (Light and Matter)