Calculadora de Potência Elétrica
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
P = V·I
About this calculator
The Electric Power Calculator is a tool that determines the power dissipated or consumed by an electrical component. It uses the three equivalent forms of Ohm's law: P = V·I, P = V²/R, and P = I²·R. The user enters two known values among voltage (V), current (I), and resistance (R), and the calculator returns power in watts. It is useful for sizing resistors, checking appliance consumption, and analyzing simple circuits.
Operation is based on fundamental electrical relationships. If you provide voltage and current, the calculation is direct: P = V × I. If voltage and resistance are entered, P = V²/R is used. With current and resistance, P = I² × R applies. The calculator also determines the missing third value if needed. For example, if you provide V and R, it calculates I = V/R and then power.
When to use? In everyday situations like finding the power of a lamp (given V and I), calculating dissipation of a resistor in an electronics project, or estimating appliance consumption. It is also helpful to verify if a component can handle the applied power, avoiding overheating. Suitable for students, technicians, and electronics enthusiasts.
Cautions: ensure units are in SI (volts, amperes, ohms). The calculator assumes constant resistance (ohmic component). For reactive loads (motors, capacitors), the calculated power is apparent, not active. It does not replace actual measurements with calibrated instruments. In AC circuits, the formula P = V·I only holds for purely resistive loads.
Frequently asked questions
What is the difference between apparent power and active power?
Apparent power is the product V·I, considering phase shift between voltage and current. Active power is the actual work done, calculated with the power factor. This calculator provides apparent power for reactive loads.
Can I use the calculator for AC circuits?
Yes, but only for purely resistive loads. For inductive or capacitive loads, the formula P = V·I does not account for phase shift, resulting in apparent power.
What if I only have power and voltage?
Enter voltage and power in the corresponding fields. The calculator determines current (I = P/V) and resistance (R = V²/P).
Does the calculator work with kilowatts, volts, and amperes?
Yes, but ensure consistent units. For example, watts for power, volts for voltage, and amperes for current. If using kW, convert to watts (1 kW = 1000 W).
How accurate are the results?
Results are accurate based on input values. However, rounding errors may occur with decimal numbers. It is recommended to use at least two decimal places.