Electrical Power Calculator
Calculate electrical power (watts), voltage, current, or resistance instantly using Ohm’s Law and standard power formulas.
Calculate Power & Resistance
Select the two values you know, enter them below, and instantly calculate the electrical power (watts) and the missing variable.
Circuit Variables
Enter your known electrical values
Circuit Evaluation
Calculated power and circuit properties
Ohm’s Law & Power Formulas
Fundamental electrical engineering formulas used in this calculator (applicable to DC and purely resistive AC circuits).
| To Find | Formula | Description |
|---|---|---|
| Power (P) | P = V × I | Power equals Voltage multiplied by Current |
| Power (P) | P = I² × R | Power equals Current squared multiplied by Resistance |
| Power (P) | P = V² / R | Power equals Voltage squared divided by Resistance |
| Voltage (V) | V = I × R | Ohm’s Law: Voltage equals Current multiplied by Resistance |
| Current (I) | I = V / R | Ohm’s Law: Current equals Voltage divided by Resistance |
| Resistance (R) | R = V / I | Ohm’s Law: Resistance equals Voltage divided by Current |
Electrical Power FAQ
Everything you need to know about calculating electrical power, voltage, current, and resistance.
Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. It is expressed as V = I × R, where V is voltage, I is current, and R is resistance.
Electrical power (P) in watts can be calculated using three main formulas depending on the known values: P = V × I (Voltage × Current), P = I² × R (Current squared × Resistance), or P = V² / R (Voltage squared ÷ Resistance).
This calculator uses formulas for DC (Direct Current) or purely resistive AC (Alternating Current) circuits. For AC circuits with inductive or capacitive loads, you must also account for the power factor (PF), using the formula P = V × I × PF.
Volts (V) measure electrical potential or pressure. Amps (A) measure the flow rate of electrical current. Ohms (Ω) measure the resistance to that flow. Watts (W) measure the actual rate of energy consumption or power output.