Power Calculator

Calculate electrical power (in watts) using voltage, current, or resistance values.

Voltage (V):

Current (I):

Resistance (R):

Power (P):

How to Use This Power Calculator

Enter any two of the following values to calculate the power:

Voltage (V) – The electrical potential difference
Current (I) – The flow of electric charge
Resistance (R) – The opposition to current flow

The calculator will automatically compute the missing values using Ohm’s Law (P = VI = I²R = V²/R).

Power Calculation Formulas

P = V × I (Power = Voltage × Current)

P = I² × R (Power = Current² × Resistance)

P = V² / R (Power = Voltage² / Resistance)

Frequently Asked Questions

What is electrical power?

Electrical power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt (W), which equals one joule per second.

How do I calculate power from voltage and current?

Power (P) equals voltage (V) multiplied by current (I): P = V × I. For example, if you have 12V and 2A, the power would be 24W.

Can I calculate power if I only know resistance and current?

Yes, you can use the formula P = I² × R, where I is current and R is resistance. For 3A through a 4Ω resistor, power would be 3² × 4 = 36W.

What’s the difference between power and energy?

Power is the rate of energy transfer (watts), while energy is power multiplied by time (watt-hours). Power is instantaneous, energy is cumulative.